Lamellipodin-Deficient Mice: A Model of Rectal Carcinoma

During a survey of clinical rectal prolapse (RP) cases in the mouse population at MIT animal research facilities, a high incidence of RP in the lamellipodin knock-out strain, C57BL/6-Raph1^tm1Fbg (Lpd^-/-) was documented. Upon further investigation, the Lpd^-/- colony was found to be infected with multiple endemic enterohepatic Helicobacter species (EHS). Lpd^-/- mice, a transgenic mouse strain produced at MIT, have not previously shown a distinct immune phenotype and are not highly susceptible to other opportunistic infections. Predominantly male Lpd^-/- mice with RP exhibited lesions consistent with invasive rectal carcinoma concomitant to clinically evident RP. Multiple inflammatory cytokines, CD11b+Gr1+ myeloid-derived suppressor cell (MDSC) populations, and epithelial cells positive for a DNA damage biomarker, H2AX, were elevated in affected tissue, supporting their role in the neoplastic process. An evaluation of Lpd^-/- mice with RP compared to EHS-infected, but clinically normal (CN) Lpd^-/- animals indicated that all of these mice exhibit some degree of lower bowel inflammation; however, mice with prolapses had significantly higher degree of focal lesions at the colo-rectal junction. When Helicobacter spp. infections were eliminated in Lpd^-/- mice by embryo transfer rederivation, the disease phenotype was abrogated, implicating EHS as a contributing factor in the development of rectal carcinoma. Here we describe lesions in Lpd^-/- male mice consistent with a focal inflammation-induced neoplastic transformation and propose this strain as a mouse model of rectal carcinoma.     

Primary care for AIDS and chemical dependence.

Primary care clinicians are acquiring an increasingly important role in preventing, diagnosing, and treating both chemical dependence and human immunodeficiency virus (HIV) illness. Towards this end they need to know the epidemiology of HIV infection in chemically dependent persons and methods of educating persons at high risk for these problems. It is critical that physicians screen for alcohol and drug addiction. Health care providers should understand the risks and benefits of HIV antibody testing and include in their practices the basic components of counseling before and after testing and informed consent. Both HIV illness and addiction are chronic diseases with long-term health implications. A knowledge of patient characteristics, intensity of treatments, and treatment modalities is important in making recommendations for individualized therapy. Combining service delivery is a future challenge necessitated by today''s joint epidemics of the acquired immunodeficiency syndrome and chemical dependence.     

The continuous positive and negative dielectrophoresis of microorganisms

The continuous dielectrophoresis of living cells is described. The technique uses stream-centered transport of suspended microorganisms through an especially shaped non-uniform electric field. The cells can be given a positive or negative displacement, i.e., can be pushed into or out of the region of higher field intensity, depending upon the frequency of the applied ac field, and upon the relative permittivities of the cells and the suspending medium. Yeast (Saccharomyces cerevisiae) and algal cells (Chlorella vulgaris) were found to provide spectra of dielectrophoretic responses varying with the applied frequency (10 to 600 kHz) and conductivity.     

A Product-Type Estimator in Double Sampling

The use of ratio and product estimators, using auxiliary information, for estimating the mean of a finite population is well known. The efficiency of ratio estimator or product estimator is high depending on whether the auxiliary character is highly positively or negatively coorelated with the main character of interest. This paper proposes a product-type estimator which is more efficient than the usual ratio and product estimators in practical situations. We consider the case of double sampling from which the single sampling results may easily be derived.     

Overexpression of a nascent polypeptide associated complex gene (SaβNAC) of Spartina alterniflora improves tolerance to salinity and drought in transgenic Arabidopsis

Salinity and drought are the most important environmental constraints limiting crop growth and productivity. Here, we have characterized a gene 'SaβNAC' encoding the β subunit of nascent polypeptide associated complex from a halophyte Spartina alterniflora and investigated its role toward abiotic stress regulation. Expression of SaβNAC was differentially regulated by abiotic stresses, including salinity, drought, cold, and ABA in leaves and roots of S. alterniflora. Constitutive over-expression of SaβNAC in Arabidopsis exhibited normal growth under non-stress conditions but enhanced tolerance to salt and drought stresses. Transgenic SaβNAC Arabidopsis retained more chlorophyll, proline, and showed improved ionic homeostasis with less damage under stress conditions compared to WT plants. This is a first report to demonstrate the involvement of βNAC in imparting abiotic stress tolerance which might be due to protection of the newly synthesized polypeptides involved in various stress tolerance mechanisms from abiotic stress induced damage and inhibition of cell death in plant.     

Cloning and expression of the gene encoding a novel proteinase from Tritirachium album limber

We have isolated the genomic and cDNA clones encoding a novel proteinase from the fungus Tritirachium album Limber, named proteinase T, synthesis of which is induced in skim milk medium. The coding sequence for this enzyme is interrupted by two introns in the fungal genome. The amino acid sequence of proteinase T as deduced from the nucleotide sequence is about 53% identical to that of proteinase K. Four cysteines are present in the mature proteinase, probably in the form of two disulfide bonds, which might explain the thermal stability of the proteinase. We have expressed the proT cDNA in Escherichia coli. The authenticity of the product has been characterized by Western blotting and N-terminal analysis of the recombinant product.     

Optimization of cellulase-free xylanase production by alkalophilic Cellulosimicrobium sp. CKMX1 in solid-state fermentation of apple pomace using central composite design and response surface methodology

Microbial xylanases and associated enzymes degrade the xylans present in lignocellulose in nature. Xylanase production by Cellulosimicrobium sp. CKMX1, isolated from mushroom compost, produced a cellulase-free extracellular endo-1, 4-β-xylanase (EC 3.2.1.8) at 35 °C and pH 8.0. Apple pomace—an inexpensive and abundant source of carbon—supported maximal xylanase activity of 500.10 U/g dry bacterial pomace (DBP) under solid state fermentation. Culture conditions, e.g., type of medium, particle size of carbon source, incubation period, temperature, initial pH, and inoculum size, were optimized and xylanase activity was increased to 535.6 U/g DBP. CMCase, avicelase, FPase and β-glucosidase activities were not detected, highlighting the novelty of the xylanase enzyme produced by CKMX1. Further optimization of enzyme production was carried out using central composite design following response surface methodology with four independent variables (yeast extract, urea, Tween 20 and carboxymethyl cellulose), which resulted in very high levels of xylanase (861.90 U/g DBP). Preliminary identification of the bacterial isolate was made on the basis of morphological and biochemical characters and confirmed by partial 16Sr RNA gene sequencing, which identified CKMX1 as Cellulosimicrobium sp. CKMX1. A phylogenetic analysis based on the 16Sr RNA gene sequence placed the isolate within the genus Cellulosimicrobium, being related most closely to Cellulosimicrobium cellulans strain AMP-11 (97% similarity). The ability of this strain to produce cost-effective xylanase from apple pomace on a large scale will help in the waste management of apple pomace.     

Escape of intracellular Shigella from autophagy requires binding to cholesterol through the type III effector,IcsB

Type III secretion systems are present in many pathogenic bacteria and mediate the translocation of bacterial effectors into host cells. Identification of host targets of these effectors is crucial for understanding bacterial virulence. IcsB, a type III secretion effector, helps Shigella to evade the host autophagy defense system by binding to the autophagy protein, Atg5. Here, we show that IcsB is able to interact specifically with cholesterol. The cholesterol binding domain (CBD) of IcsB is located between residues 288 and 351. Specific mutations of single tyrosine residues Y297 or Y340 of IcsB by phenylalanine (F) slightly reduced cholesterol binding, whereas deletion of the entire CBD or double mutation Y297F-Y340F strongly abolished interactions with cholesterol. To determine whether Shigella expressing IcsB variants could evade autophagy as effectively as the wild-type Shigella, we infected MDAMC cells stably expressing the autophagy marker LC3 fused to GFP and bacterial autophagosome formation was quantified using fluorescence microscopy. Mutation Y297F or Y340F slightly impaired IcsB function, whereas complete removal of CBD or mutation Y297F-Y340F significantly impaired autophagy evasion. Furthermore, we report that BopA, the counterpart of IcsB in Burkholderia pseudomallei with similar autophagy-evading properties, contains the CBD domain and is also able to bind cholesterol.     

Fibre bundle element method of determining physiological cross-sectional area from three-dimensional computer muscle models created from digitised fibre bundle data

Physiological cross-sectional area (PCSA) is used to compare force-producing capabilities of muscles. A limitation of PCSA is that it cannot be measured directly from a specimen, as there is usually no area within the muscle traversed by all fibres. Traditionally, a formula requiring averaged architectural parameters has been used. The purpose of this paper is to describe the development of a fibre bundle element (FBE) method to calculate PCSA from digitised fibre bundle data of five architecturally distinct muscles and compare the FBE and PCSA formula. An FBE method was developed that used a serially arranged set of cylinders as the volumetric representation of each fibre bundle, and PCSA was computed as the summation of the cross-sectional area of each FBE. Four of five muscles had significantly different PCSA between FBE and formula methods. The FBE method provides an approach that considers architectural variances while minimising the need for averaged architectural parameters.