Overexpression of a membrane transport system MSMEG_1381 and MSMEG_1382 confers multidrug resistance in Mycobacterium smegmatis

Mycobacterium tuberculosis is a leading cause of human mortality worldwide, and the emergence of drug-resistant strains demands the discovery of new classes of antimycobacterial that can be employed in the therapeutic pipeline. Previously, a secondary metabolite, chrysomycin A, isolated from Streptomyces sp. OA161 displayed potent bactericidal activity against drug-resistant clinical isolates of M. tuberculosis and different species of mycobacteria. The antibiotic inhibits mycobacterial topoisomerase I and DNA gyrase, leading to bacterial death, but the mechanisms that could cause resistance to this antibiotic are currently unknown. To further understand the resistance mechanism, using M. smegmatis as a model, spontaneous resistance mutants were isolated and subjected to whole-genome sequencing. Mutation in a TetR family transcriptional regulator MSMEG_1380 was identified in the resistant isolates wherein the gene was adjacent to an operon encoding membrane proteins MSMEG_1381 and MSMEG_1382. Sequence analysis and modeling studies indicated that MSMEG_1381 and MSMEG_1382 are components of the Mmp family of efflux pumps and over-expression of either the operon or individual genes conferred resistance to chrysomycin A, isoniazid, and ethambutol. Our study highlights the role of membrane transporter proteins in conferring multiple drug resistance and the utility of recombinant strains overexpressing membrane transporters in the drug screening pipeline.

B1CTcu5: A frog-derived brevinin-1 peptide with anti-tuberculosis activity

Tuberculosis (TB) is a devastating infectious disease that causes a high rate of mortality. Drugs with new modes of action are needed to overcome this scenario. Cationic antibacterial peptides can serve as a potential alternative to existing TB drugs as they target the entire bacterial membrane for activity, thereby reducing the probability of development of drug resistance. In this study, we report anti-tuberculosis activity of B1CTcu5, a peptide that belongs to brevinin-1 family of antimicrobial peptides. This peptide possesses potent in vitro inhibitory activity against M. tuberculosis at 12.5 μg/mL but was not active against M. smegmatis. B1CTcu5 successfully eliminated intracellular mycobacteria without inducing cytotoxicity to the human macrophages at the concentrations tested. This peptide can be used as a template to design peptide-based anti-tubercular agents.

Molecular Networking and Whole-Genome Analysis Aid Discovery of an Angucycline That Inactivates mTORC1/C2 and Induces Programmed Cell Death

Rediscovery of known compounds and time consumed in identification, especially high molecular weight compounds with complex structure, have let down interest in drug discovery. In this study, whole-genome analysis of microbe and Global Natural Products Social (GNPS) molecular networking helped in initial understanding of possible compounds produced by the microbe. Genome data revealed 10 biosythethic gene clusters that encode for secondary metabolites with anticancer potential. NMR analysis of the pure compound revealed the presence of a four-ringed benz[a]anthracene, thus confirming angucycline; molecular networking further confirmed production of this class of compounds. The type II polyketide synthase gene identified in the microbial genome was matched with the urdamycin cluster by BLAST analysis. This information led to ease in identification of urdamycin E and a novel natural derivative, urdamycin V, purified from Streptomyces sp. OA293. Urdamycin E (Urd E) induced apoptosis and autophagy in cancer cell lines. Urd E exerted anticancer action through inactivation of the mTOR complex by preventing phosphorylation at Ser 2448 and Ser 2481 of mTORC1 and mTORC2, respectively. Significant reduction in phosphorylation of the major downstream regulators of both mTORC1 (p70s6k and 4e-bp1) and mTORC2 (Akt) were observed, thus further confirming complete inhibition of the mTOR pathway. Urd E presents itself as a novel mTOR inhibitor that employs a novel mechanism in mTOR pathway inhibition.

Streptomyces sp metabolite(s) promotes Bax mediated intrinsic apoptosis and autophagy involving inhibition of mTOR pathway in cervical cancer cell lines

In cervical cancer, the association between HPV infection and dysregulation of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway (PI3K/AKT/mTOR pathway) places mTOR as an attractive therapeutic target. The failure of current treatment modalities in advanced stages of this cancer and drawbacks of already available mTOR inhibitors demand for novel drug candidates. In the present study we identified the presence of a mTOR inhibitor in an active fraction of the ethyl acetate extract of Streptomyces sp OA293. The metabolites(s) in the active fraction completely inhibited mTORC1 and thereby suppressed activation of both of its downstream targets, 4E-BP1 and P70S6k, in cervical cancer cells. In addition, it also stalled Akt activation via inhibition of mTORC2. The mechanism of mTOR inhibition detailed in our study overcomes significant drawbacks of well known mTOR inhibitors such as rapamycin and rapalogs. The active fraction induced autophagy and Bax mediated apoptosis suggesting that mTOR inhibition resulted in programmed cell death of cancer cells. The molecular weight determination of the components in active fraction confirmed the absence of any previously known natural mTOR inhibitor. This is the first report of complete mTOR complex inhibition by a product derived from microbial source.

Development of a Novel Herbal Formulation To Inhibit Biofilm Formation in Toxigenic Vibrio cholerae

Vibrio cholerae, a causative agent of the waterborne disease cholera, still threatens a large proportion of world's population. The role of biofilm formation in V. cholerae pathogenesis is well established, as it provides the bacterium enhanced tolerance to antimicrobial agents and increased transmission. In the present study, four medicinal plants used in traditional medicines with antidiarrheal properties were evaluated for its antibiofilm activity. Methanol extracts of these plants (Centella asiatica, Elephantopus scaber, Camellia sinensis, and Holarrhena antidysenterica) showed promising antibiofilm activity against V. cholerae with crystal violet and air-liquid interface coverslip assays. Results revealed that C. asiatica, E. scaber, C. sinensis, and H. antidysenterica extracts significantly inhibited biofilm formation by approximately 75, 76, 78, and 55% at concentrations of 3, 2, 1, and 0.6 mg/mL, respectively. A promising antibiofilm activity of ∼89% inhibition at 1.5 mg/mL concentration was observed when a combination of E. scaber and C. sinensis was used. The herbal extracts were thermostable at a temperature range of 40 to 100°C. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay revealed that the viability of bacteria was not affected by treatment with these plant extracts. Gene expression studies revealed that extracts of H. antidysenterica leaf, H. antidysenterica bark, and the whole plant of E. scaber and C. asiatica down-regulate aphA or aphB, the major regulator genes modulating both virulence and biofilm formation. Hence, we propose that these herbal combinations could serve as a multifaceted approach to combat the pathogen and also, in turn, reduce antimicrobial resistance development.

Mycobacterium tuberculosis Infection Induces HDAC1-Mediated Suppression of IL-12B Gene Expression in Macrophages

Downregulation of host gene expression is one of the many strategies employed by intracellular pathogens such as Mycobacterium tuberculosis (MTB) to survive inside the macrophages and cause disease. The underlying molecular mechanism behind the downregulation of host defense gene expression is largely unknown. In this study we explored the role of histone deacetylation in macrophages in response to infection by virulent MTB H37Rv in manipulating host gene expression. We show a significant increase in the levels of HDAC1 with a concomitant and marked reduction in the levels of histone H3-acetylation in macrophages containing live, but not killed, virulent MTB. Additionally, we show that HDAC1 is recruited to the promoter of IL-12B in macrophages infected with live, virulent MTB, and the subsequent hypoacetylation of histone H3 suppresses the expression of this gene which plays a key role in initiating Th1 responses. By inhibiting immunologically relevant kinases, and by knockdown of crucial transcriptional regulators, we demonstrate that protein kinase-A (PKA), CREB, and c-Jun play an important role in regulating HDAC1 level in live MTB-infected macrophages. By chromatin immunoprecipitation (ChIP) analysis, we prove that HDAC1 expression is positively regulated by the recruitment of c-Jun to its promoter. Knockdown of HDAC1 in macrophages significantly reduced the survival of intracellular MTB. These observations indicate a novel HDAC1-mediated epigenetic modification induced by live, virulent MTB to subvert the immune system to survive and replicate in the host.

Resveratrol--a potential inhibitor of biofilm formation in Vibrio cholerae

Resveratrol, a phytochemical commonly found in the skin of grapes and berries, was tested for its biofilm inhibitory activity against Vibrio cholerae. Biofilm inhibition was assessed using crystal violet assay. MTT assay was performed to check the viability of the treated bacterial cells and the biofilm architecture was analysed using confocal laser scanning microscopy. The possible target of the compound was determined by docking analysis. Results showed that subinhibitory concentrations of the compound could significantly inhibit biofilm formation in V. cholerae in a concentration-dependent manner. AphB was found to be the putative target of resveratrol using docking analysis. The results generated in this study proved that resveratrol is a potent biofilm inhibitor of V. cholerae and can be used as a novel therapeutic agent against cholera. To our knowledge, this is the first report of resveratrol showing antibiofilm activity against V. cholerae.

Vaccine delivery system for tuberculosis based on nano-sized hepatitis B virus core protein particles

Nano-sized hepatitis B virus core virus-like particles (HBc-VLP) are suitable for uptake by antigen-presenting cells. Mycobacterium tuberculosis antigen culture filtrate protein 10 (CFP-10) is an important vaccine candidate against tuberculosis. The purified antigen shows low immune response without adjuvant and tends to have low protective efficacy. The present study is based on the assumption that expression of these proteins on HBc nanoparticles would provide higher protection when compared to the native antigen alone. The cfp-10 gene was expressed as a fusion on the major immunodominant region of HBc-VLP, and the immune response in Balb/c mice was studied and compared to pure proteins, a mixture of antigens, and fusion protein-VLP, all without using any adjuvant. The humoral, cytokine, and splenocyte cell proliferation responses suggested that the HBc-VLP bearing CFP-10 generated an antigen-specific immune response in a Th1-dependent manner. By virtue of its self-adjuvant nature and ability to form nano-sized particles, HBc-VLPs are an excellent vaccine delivery system for use with subunit protein antigens identified in the course of recent vaccine research.

A novel site of insertion of IS6110 in the moaB3 gene of a clinical isolate of Mycobacterium tuberculosis

In Mycobacterium tuberculosis, genomic variation is generated mainly by insertions and deletions rather than by point mutations. RvD5 is one such deletion in M. tuberculosis H37Rv. Previous studies from our laboratory have shown the presence of moaA3 gene in the RvD5 region in a large number of clinical isolates, that is absent in M. tuberculosis H37Rv and H37Ra. The present study was aimed at investigating the RvD5 locus of the clinical isolates by a detailed PCR analysis. Here we report a new point of insertion of the mobile genetic element, IS6110 in the genome of one clinical isolate of M. tuberculosis. The insertion has disrupted the moaB3 gene, one of the ORFs in the RvD5 region, which is involved in the molybdopterin biosynthetic pathway. This insertion of IS6110 in the moaB3 of the clinical isolate is different when compared to the insertion in the moaB3 gene of M. tuberculosis H37Rv where 4kb RvD5 region has been lost by homologous recombination and only a truncated form of the gene is present. This finding is of relevance since IS6110 is a major element determining the genome plasticity of M. tuberculosis and its numerical and positional polymorphism has always been of special interest.

Ethyl p-methoxycinnamate isolated from a traditional anti-tuberculosis medicinal herb inhibits drug resistant strains of Mycobacterium tuberculosis in vitro

Many plants are used in Ayurveda for the treatment of tuberculosis. Our aim was to examine if these plants possess any specific molecule that inhibits Mycobacterium tuberculosis. One of them, Kaempferia galanga, yielded an anti-TB molecule, ethyl p-methoxycinnamate (EPMC). By resazurin microtitre assay (REMA), EPMC was shown to inhibit M. tuberculosis H37Ra, H37Rv, drug susceptible and multidrug resistant (MDR) clinical isolates (MIC 0.242-0.485mM). No cross resistance was observed to any standard anti-TB drugs in the MDR strains. The compound did not inhibit any prototype bacteria tested. EPMC seems to be a potential anti-TB lead molecule.

Drug resistance in Mycobacterium tuberculosis isolates from tuberculosis patients in Kerala, India

OBJECTIVE

To analyse the extent of drug resistance in clinical isolates of Mycobacterium tuberculosis from patients attending various tuberculosis (TB) clinics in Kerala, India.

DESIGN

Mycobacteria were isolated from sputum samples of TB patients. Isolates from 92 new and 104 retreatment cases were tested for resistance to four first-line drugs (isoniazid, rifampicin, ethambutol and streptomycin).

RESULTS

Twenty-three per cent of the isolates from new cases and 14% from retreatment cases were pan-susceptible, and the rest were resistant to at least one of the drugs. Multidrug-resistant isolates accounted for 5.4% among new cases and 16.4% among retreatment cases. It should be noted that 18.5% of the isolates were mycobacteria other than tuberculosis.

CONCLUSION

There is an urgent need for statewide surveys to assess the level of drug resistance using quality-assured culture and drug susceptibility services. Considering that the Revised National TB Control Programme in India has been made operational nationwide, this kind of screening should be made mandatory under the programme to effectively control the spread of TB.

Predictive value of IL-18 and SC5b-9 for neurocognitive dysfunction after cardiopulmonary bypass

BACKGROUND

Neurological injury after cardiopulmonary bypass (CPB) continues to be a major problem after cardiac surgery. The aim of this study was to investigate the predictive value of Interleukin-18 (IL-18) and SC5b-9 as biochemical markers of neurocognitive dysfunction after cardiac surgery.

METHODS

A total of 30 patients undergoing elective cardiac surgery using CPB were recruited. Blood samples were obtained for IL-18 and SC5b-9 concentrations before induction, 24, 48, 72, 96 and 120 h post-CPB and 6 weeks after operation. In addition, patients underwent a standard battery of neuropsychometric tests before operation and at day 5 and 6 weeks after operation.

RESULTS

Serum concentration of IL-18, but not SC5b-9, was significantly different between patients with and without neurocognitive dysfunction; serum IL-18 concentration significantly increased in patients with neurocognitive dysfunction (P = 0.018). Neurological outcome was significantly dependent on peak difference in IL-18 concentration at day 5 (P = 0.033), but not on peak difference in SC5b-9 concentration (P = 0.16). Eight patients had neurocognitive dysfunction at day 5 and three had neurocognitive dysfunction at 6 weeks. In a very small number of patients, no significant association was demonstrated between IL-18 or SC5b-9 concentrations and neurocognitive dysfunction at 6 weeks.

CONCLUSIONS

IL-18 has the potential as a useful marker of neurological dysfunction, requiring further investigation.

Left ventricular systolic dysfunction identification by motion analysis

This paper presents a new technique for identification of regional dysfunctions in the left ventricle from 2-D echocardiography. It uses a novel left ventricular border tracking algorithm based on Fuzzy inference system. In this paper we show how the regional dysfunction present in the left ventricle can be identified by tracking the movement of centre of mass of left ventricle in a 2D space. The path pattern of that point traced over the cardiac cycles shows variation between the two groups. The main advantage of this proposed approach is the smaller date handling in regional dysfunction identifications unlike other existing methods. The method is illustrated on the real 2D echocardiograph dataset that includes patients having dysfunctions in the left ventricular wall. The diagnostic potential of this method is explained in detail.

Interaction of papillomavirus E2 protein with the Brm chromatin remodeling complex leads to enhanced transcriptional activation

Papillomavirus E2 is a sequence-specific DNA binding protein that regulates transcription and replication of the viral genome. The transcriptional activities of E2 are typically evaluated by transient transfection of nonreplicating E2-dependent reporters. We sought to address whether E2 activates transcription in an episomal context and its potential interaction with the chromatin remodeling proteins. Using an Epstein-Barr virus-based episomal reporter, we demonstrate that E2 stimulates transcription from an E2-dependent promoter in a chromatin context. This activation is enhanced by the presence of proteins associated with SWI/SNF complexes, which are ATP-dependent chromatin remodeling enzymes. We show that exogenous expression of the Brm ATPase enhances E2 activity in SWI/SNF-deficient cell lines and that the amino-terminal transactivation domain of E2 mediates association with the Brm complex in vivo. Using chromatin immunoprecipitation assays, we demonstrate that Brm enhances promoter occupancy by E2 in an episomal context. Our results demonstrate that E2 activates transcription from an episomal reporter system and reveal a novel property of E2 in collaborating with the Brm chromatin remodeling complex in enhancing transcriptional activation.

Mutation and evolutionary analyses identify NR2E1-candidate-regulatory mutations in humans with severe cortical malformations

Nuclear receptor 2E1 (NR2E1) is expressed in human fetal and adult brains; however, its role in human brain–behavior development is unknown. Previously, we have corrected the cortical hypoplasia and behavioral abnormalities in Nr2e1^−/− mice using a genomic clone spanning human NR2E1, which bolsters the hypothesis that NR2E1 may similarly play a role in human cortical and behavioral development. To test the hypothesis that humans with abnormal brain–behavior development may have null or hypomorphic NR2E1 mutations, we undertook the first candidate mutation screen of NR2E1 by sequencing its entire coding region, untranslated, splice site, proximal promoter and evolutionarily conserved non-coding regions in 56 unrelated patients with cortical disorders, namely microcephaly. We then genotyped the candidate mutations in 325 unrelated control subjects and 15 relatives. We did not detect any coding region changes in NR2E1; however, we identified seven novel candidate regulatory mutations that were absent from control subjects. We used in silico tools to predict the effects of these candidate mutations on neural transcription factor binding sites (TFBS). Four candidate mutations were predicted to alter TFBS. To facilitate the present and future studies of NR2E1, we also elucidated its molecular evolution, genetic diversity, haplotype structure and linkage disequilibrium by sequencing an additional 94 unaffected humans representing Africa, the Americas, Asia, Europe, the Middle East and Oceania, as well as great apes and monkeys. We detected strong purifying selection, low genetic diversity, 21 novel polymorphisms and five common haplotypes at NR2E1. We conclude that protein-coding changes in NR2E1 do not contribute to cortical and behavioral abnormalities in the patients examined here, but that regulatory mutations may play a role.

Quantitative Evaluation of Left Ventricle Performance from Two Dimensional Echo Images

OBJECTIVES

We sought to quantify the left ventricle systolic dysfunction by a geometric index from two-dimensional (2D) echocardiography by implementing an automated fuzzy logic edge detection algorithm for the segmentation.

BACKGROUND

The coronary injuries have repercussions on the left ventricle producing changes on wall contractility, the shape of the cavity, and as a whole changes on the ventricular function.

METHODS

2D echocardiogram and M-mode recordings were performed over the control group and those with the dysfunctions. From 2D recordings, individual frames were extracted for at least five cardiac cycles and then segmentation of left ventricle was done by automated fuzzy systems. In each frame, the volumes are measured and a geometric index, eccentricity ratio (ER), was derived. The endocardial fractional shortening (FS), midwall fractional shortening (mFS), and the relative wall thickness (RWT) were also measured in each case.

RESULTS

Depressed value of endocardial FS (20.39 +/- 5.43 vs 34.28 +/- 9.36, P = 0.0046), mFS (33 +/- 8.3 vs 52.5 +/- 11.7, P = 0.0047), and the RWT (0.337 +/- 0.096 vs 0.525 +/- 0.119, P = 0.0002) was observed with dysfunction. ER measured at end-diastole (2.86 +/- 0.703 vs 4.14 +/- 0.38) and end-systole (3.14 +/- 0.79 vs 5.48 +/- 0.74) was found to be decreased in the dysfunction group and more significant at the end-systole (P = 0.00017 vs 6.6E-06).

CONCLUSION

This work concludes that the regional and global left ventricle systolic dysfunction can be assessed by the ER measured at end-diastole and end-systole from 2D echocardiogram and may contribute to the high rate of cardiovascular disorders.

Detection of left ventricle systolic dysfunction from shape deformity

Coronary artery disease producing ischemic cardiomyopathy is the most frequent cause of left ventricular systolic dysfunction. Non-ischemic cardiomyopathies can also produce systolic dysfunction; they may be inherited as genetic disorders or occur sporadically. These coronary injuries have repercussions on the left ventricle producing changes on wall contractility, the shape of the cavity and also changes on ventricular function. This study is focused on the 2D echocardiograms of the left ventricle. Apical two chamber and four chamber view recordings were performed on normal and systolic dysfunction subjects. Individual frames were extracted for at least five cardiac cycles. After pre-processing these images, segmentation of the left ventricle was performed by Fuzzy systems. Then the volumes were measured by single and biplane methods along with the perimeter, short axis length and long axis length in each frame, from which the two indices Sphericity Index (SI) and Normalized Eccentricity Index (NEI) was determined. It was found that the diastolic phase is short in the case of systolic dysfunction, and its volume variation is not uniform as in the normal case. Also, in the case of systolic dysfunction, the span of either the long or short axis length variation is less than 0.5 cm. This depicts that akinesis is in the corresponding direction; the value of SI is less than 2 for systolic dysfunction. A sharp peak is seen at each systole point in the NEI plot and also its variation is smooth in subjects having LVEF > 45%, which is not the case for dysfunction.

Intrafamilial correlation of clinical manifestations in neurofibromatosis 2 (NF2)

Measuring correlation in clinical traits among relatives is important to our understanding of the causes of variable expressivity in Mendelian diseases. Random effects models are widely used to estimate intrafamilial correlations, but such models have limitations. We incorporated survival techniques into a random effects model so that it can be used to estimate intrafamilial correlations in continuous variables with right censoring, such as age at onset. We also describe a negative-binomial gamma mixture model to determine intrafamilial correlations of discrete (e.g., count) data. We demonstrate the utility of these methods by analyzing intrafamilial correlations among patients with neurofibromatosis 2 (NF2), an autosomal-dominant disease caused by mutations of the NF2 tumor-suppressor gene. We estimated intrafamilial correlations in age at first symptom of NF2, age at onset of hearing loss, and number of intracranial meningiomas in 390 NF2 nonprobands from 153 unrelated families. A significant intrafamilial correlation was observed for each of the three features: age at onset (0.35; 95% confidence interval (CI) 0.23-0.47), age at onset of hearing loss (0.51; 95% CI, 0.35-0.64), and number of meninginomas (0.29; 95% CI, 0.15-0.43). Significant correlations were also observed for age at first symptom within NF2 families with truncating mutations (0.41; 95% CI, 0.06-0.68) or splice-site mutations (0.29; 95% CI, 0.03-0.51), for age at onset of hearing loss within families with missense mutations (0.67; 95% CI, 0.18-0.89), and for number of meningiomas within families with splice-site mutations (0.39; 95% CI, 0.13-0.66). Our findings are consistent with effects of both allelic and nonallelic familial factors on the clinical variability of NF2.

Experimental studies on a new bioactive material: HAIonomer cements

The lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents has resulted in the development of glass ionomer cements (GICs) for biomedical applications. In order to improve biocompatibility and biomechanically match GICs to bone, hydroxyapatite-ionomer (HAIonomer) hybrid cements were developed. Ultra-fine hydroxyapatite (HA) powders were produced using a new induction spraying technique that utilizes a radio-frequency source to spheriodize an atomized suspension containing HA crystallites. The spheriodized particulates were then held at 800 degrees C for 4 h in a carbolite furnace using a heating and cooling rate of 25 degrees C/min to obtain almost fully crystalline HA powders. The heat-treated particles were characterized and introduced into a commercial glass ionomer cement. 4 (H4), 12 (H12) and 28 (H28) vol% of fluoroalumino silicate were substituted by crystalline HA particles that were dispersed using a high-speed dispersion technique. The HAIonomer cements were subjected to hardness, compressive and diametral tensile strength testing based upon BS6039:1981. The storage time were extended to one week to investigate the effects of cement maturation on mechanical properties. Commercially available capsulated GIC (GC) and GIC at maximum powder:liquid ratio (GM) served as comparisons. Results were analyzed using factorial ANOVA/Scheffe's post-hoc tests and independent samples t-test at significance level 0.05. The effect of time on hardness was material dependent. With the exception of H12, a significant increase in hardness was observed for all materials at one week. A significant increase in compressive strength was, however, observed for H12 over time. At 1 day and 1 week, the hardness of H28 was significantly lower than for GM, H4, and H12. No significant difference in compression and diametral tensile strengths were observed between materials at both time intervals. Results show that HAIonomers is a promising material, which possess good mechanical properties. Potential uses of this new material include bone cements and performed implants for hard tissue replacement in the field of otological, oral-maxillofacial and orthopedic surgery.

Serum and tissue glycoconjugates, digoxin and magnesium levels in chronic calcific pancreatitis

BACKGROUND

Endogenous or exogenous digoxin can lead to membrane Na+,K+-ATPase inhibition and hypomagnesemia. Low magnesium levels can lead to increased glycosaminoglycans (GAG) concentration in many organs.

AIM

To measure the serum levels of pancreatic GAG and glycoproteins, two major components of the extracellular matrix, in patients with chronic calcific pancreatitis (CCP). Serum levels of magnesium and digoxin were also assessed.

METHODS

Patients with CCP and age- and sex-matched healthy control subjects (15 each) were studied. Serum GAG, Mg and digoxin levels were measured. RBC membrane Na+,K+-ATPase activity was also assessed. Pancreatic tissue obtained at autopsy from seven patients with CCP and sex- and age-matched healthy subjects who had died in accidents were also tested for GAG and glycoproteins.

RESULTS

Total GAG levels were significantly increased in the serum and pancreas of patients with CCP. This was associated with lower serum Mg levels, increased serum digoxin levels and decreased RBC membrane Na+,K+-ATPase activity.

CONCLUSION

Exogenous or endogenous digoxin-induced hypomagnesemia and the consequent altered glycoconjugate metabolism may be important in the pathogenesis of CCP.

Genetics of anesthetic response: autosomal mutations that render Drosophila resistant to halothane

Molecular mechanisms of anesthetic action are poorly understood. Genetic approaches to investigate mechanisms of anesthesia, although sparse and rather new, are turning out to be informative and add a new perspective. Before beginning a systematic investigation of anesthesia by this approach, it is necessary to have at hand a large collection of mutations in different loci that alter anesthetic response. We report here the isolation and characterization of six mutant autosomal lines that show a decreased sensitivity to the inhalation of anesthetic halothane. Two of these mutations, Omar(82) and Qajjem(211) are shown to map to separate loci on the third chromosome.

Biodegradation of tannic acid by Citrobacter freundii isolated from a tannery effluent

A bacterial strain capable of utilizing tannic acid as sole carbon source was isolated from the effluent of a tannery and was identified as Citrobacter freundii. This organism could grow at concentrations as high as 5% (w/v) of tannic acid and produced extracellular tannase to hydrolyze the same. When grown in minimal medium containing 1% tannic acid (w/v) at 30 degrees C, this strain produced 1.87 U/ml of tannase at 6 h. At that time, tannic acid degradation products, namely glucose and gallic acid, were detectable in the culture filtrate; the other intermediate metabolites formed were pyrogallol (extracellular) and pyruvate (intracellular). 2-hydroxymuconic acid is presumed to form as a result of ortho-cleavage of pyrogallol. The proposed biochemical pathway for the degradation of tannic acid by Citrobacter freundii is: Tannic acid-->[Glucose + Gallic acid]-->Pyrogallol -->2-hydroxymuconic acid -->[?]-->Pyruvate.

New features and enhancements in the X-PLOR computer program

This article describes new methods for X-ray crystallographic refinement and nuclear magnetic resonance (NMR) structure determination that are available in the recent release of the X-PLOR software, X-PLOR 98.0. The major new features of the X-PLOR 98.0 software are: (i) the introduction of maximum likelihood methods (Pannu and Read, Acta Crystallogr 1996;A52:659-668) for X-ray crystallographic refinement with structure factor amplitude, intensity and phase probability targets, (ii) the addition of the Andersen thermal coupling method for temperature control during simulated annealing refinements, (iii) a new utility function for converting reflection data in to the X-PLOR format, (iv) validated scripts and performance enhancements for structure determination from NMR distance restraints using torsion angle dynamics, (v) fast code for direct nuclear Oberhauser effect (NOE) refinement using matrix doubling and gaussian quadratures, (vi) methodologies for using ambiguous restraint information to perform automated iterative peak assignment and structure determination (Nilges et al., J Mol Biol 1997;269: 408-422). Additional developments in methodology for refining crystal structures from poor initial models include the implementation of a fast adaptive bulk solvent scattering correction and an energy minimization routine that makes use of second derivative information. Trial crystallographic refinements with an energy minimization protocol that includes these enhancements indicate significantly improved convergence. The quality of the resulting models appears comparable to models obtained from refinement protocols that incorporate torsion angle dynamics. Test applications of the new energy minimizer to NMR structure refinement with using NOE calculations also show improved convergence, leading to more optimized final models.

Probing cell-surface architecture through synthesis: an NMR-determined structural motif for tumor-associated mucins

Cell-surface mucin glycoproteins are altered with the onset of oncogenesis. Knowledge of mucin structure could be used in vaccine strategies that target tumor-associated mucin motifs. Thus far, however, mucins have resisted detailed molecular analysis. Reported herein is the solution conformation of a highly complex segment of the mucin CD43. The elongated secondary structure of the isolated mucin strand approaches the stability of motifs found in folded proteins. The features required for the mucin motif to emerge are also described. Immunocharacterization of related constructs strongly suggests that the observed epitopes represent distinguishing features of tumor cell-surface architecture.

Spontaneous anti-Stokes Raman probe for gas temperature measurements in industrial furnaces

A compact, pulsed Nd:YAG laser-based instrument has been built to measure in situ absolute gas temperatures in large industrial furnaces by use of spontaneous anti-Stokes Raman scattering. The backscattering configuration was used to simplify the optics alignment and increase signal-to-noise ratios. Gated signal detection significantly reduced the background emission that is found in combustion environments. The anti-Stokes instead of the Stokes component was used to eliminate contributions to spectra from cold atmospheric nitrogen. The system was evaluated in a methane/air flame and in a bench-top oven, and the technique was found to be a reliable tool for nonintrusive absolute temperature measurements with relatively clean gas streams. A water-cooled insertion probe was integrated with the Raman system for measurement of the temperature profiles inside an industrial furnace. Gas temperatures near 1500-1800 K at atmospheric pressure in an industrial furnace were inferred by fitting calculated profiles to experimental spectra with a standard deviation of less than 1% for averaging times of approximately 200 s. The temperatures inferred from Raman spectra are in good agreement with data recorded with a thermocouple probe.

Quantitative model for Gal4p-mediated expression of the galactose/melibiose regulon in Saccharomyces cerevisiae

A mathematical model based on equilibrium binding between Gal4p and its specific DNA binding site has been developed. A model for GAL gene expression solely due to cooperativity, as a function of Gal4p concentration, has been developed for a gal80 mutant. The above model was extended to include other known regulatory molecules, namely Gal80p and Gal3p. Parameters determined from the above simulation were then used to represent a physiological status of gene expression in response to glucose (in terms of Gal4p concentration) and galactose in a wild-type strain. We demonstrate that in a wild-type strain glucose repression is more stringent due to cooperativity and autogenous regulation, while the induction response to galactose is only through autogenous regulation. The biological significance of autogenous regulation in Saccharomyces cerevisiae is discussed vis-a-vis the lactose operon of Escherichia coli.