The role of mutation accumulation in HIV progression

The onset of AIDS is characterized by the collapse of the immune system after a prolonged asymptomatic period. The mechanistic basis of this disease progression has remained obscure, hindering the development of effective therapies. Here I present a mechanism that underlies the deterioration of the immune system during HIV infection. The elevated turnover of lymphocytes throughout the asymptomatic period is postulated to result in the accumulation of deleterious mutations, which impairs immunological function, replicative ability and viability of lymphocytes. This mutational meltdown is proposed to occur throughout the hierarchy of lymphocyte progenitors, resulting in the deterioration of lymphocyte regeneration and an ensuing rise in viral loads. A mathematical model is used to illustrate this mechanism of progressive immunological deterioration. Mutation accumulation may explain not only the decline in CD4+T cells, but also the functional deterioration of CD4+T cells, CD8+T cells and B cells, and the exhaustion of lymphocyte regeneration.     

Influence of surface shape on DNA binding of bimetallo helicates

In order to probe the DNA-helicate interactions responsible for the DNA binding and remarkable changes of the DNA secondary structure induced by a tetracationic bi-metallo helicate [Fe(2)(L(1))(3)](4+) (L(1)=C(25)H(20)N(4)), we have designed and synthesised derivatives with hydrophobic methyl groups at different positions on the ligand backbone. Two dimetallo helicates [Fe(2)(L(i))(3)](4+) were prepared using ligands L(3) and L(5) with the methyl substituent on, respectively, the 3 and 5 positions of the pyridyl ring thus producing a wider or slightly longer tetracationic DNA binder. UV/visible absorbance, circular and linear dichroism spectroscopies have been used to characterize the interactions of the cylinders with DNA with the aim of investigating any sequence preference or selectivity upon binding. Competitive binding studies using fluorescent dyes Hoechst 33258 (a minor groove binder), ethidium bromide (an intercalator) and a major groove binding cation (cobalt (III) hexammine) which induces the B-->Z transition have been employed to determine the binding geometries of the enantiomers of two methylated helicates (L(3) and L(5)) to DNA and compare with the data obtained previously for the unmethylated analogue (L(1)). The results demonstrate that the racemic mixtures and the resolved enantiomers of all helicates bind to DNA inducing structural changes. The overall conclusion from the effect of adding these groups to the surface of the parent helicate is that increasing the width (L(3)) reduces the DNA binding strength, the bending and coiling effect and the groove selectivity of the enantiomers compared with the parent compound. There is limited evidence to suggest a slight GC sequence preference. Lengthening the helicate (L(5)) results in DNA interactions similar to those of the parent compounds, with an increased preference of the P enantiomer for the minor groove indicating an enhancement of mode selectivity.     

Metal biosorption in lignocellulosic biofuel biorefinery effluent: an initial step towards sustainability of water resources

Biosorption of metals by microorganisms is a promising technology to remove accumulated non-process elements in highly recycled biorefinery process water. Removal of these elements would enable greater water reuse and reduce the environmental impact of effluent discharge. A model lignocellulosic ethanol biorefinery wastewater was created based on pulp mill effluent. This generated a wastewater with an environmentally realistic high loading of dissolved natural organic matter (900?mg/l), a potentially important factor influencing metal biosorption. Analysis of feedstock and pulp mill effluent indicated that Mn and Zn are likely to be problematic in highly recycled lignocellulosic ethanol biorefinery process water. Therefore, the growth of several bacteria and fungi from existing collections, and some isolated from pulp mill effluent were tested in the model wastewater spiked with Mn and Zn (0.2?mM). Wastewater isolates grew the best in the wastewater. Metal uptake varied by species and was much greater for Zn than Mn. A bacterium, Novosphingobium nitrogenifigens Y88(T), removed the most metal per unit biomass, 35 and 17?mg?Mn/g. No other organism tested decreased the Mn concentration. A yeast, Candida tropicalis, produced the most biomass and removed the most total metal (38?% of Zn), while uptake per unit biomass was 24?mg?Zn/g. These results indicate that microorganisms can remove significant amounts of metals in wastewater with high concentrations of dissolved natural organic matter. Metal sorption by autochthonous microorganisms in an anaerobic bioreactor may be able to extend water reuse and therefore lower the water consumption of future biorefineries.     

Wolbachia Reduces the Transmission Potential of Dengue-Infected Aedes aegypti

BackgroundDengue viruses (DENV) are the causative agents of dengue, the world’s most prevalent arthropod-borne disease with around 40% of the world’s population at risk of infection annually. Wolbachia pipientis, an obligate intracellular bacterium, is being developed as a biocontrol strategy against dengue because it limits replication of the virus in the mosquito. The Wolbachia strain wMel, which has been introduced into the mosquito vector, Aedes aegypti, has been shown to invade and spread to near fixation in field releases. Standard measures of Wolbachia’s efficacy for blocking virus replication focus on the detection and quantification of virus in mosquito tissues. Examining the saliva provides a more accurate measure of transmission potential and can reveal the extrinsic incubation period (EIP), that is, the time it takes virus to arrive in the saliva following the consumption of DENV viremic blood. EIP is a key determinant of a mosquito’s ability to transmit DENVs, as the earlier the virus appears in the saliva the more opportunities the mosquito will have to infect humans on subsequent bites.Conclusions/SignificanceThe saliva-based traits reported here offer more disease-relevant measures of Wolbachia’s effects on the vector and the virus. The lengthening of EIP highlights another means, in addition to the reduction of infection frequencies and DENV titers in mosquitoes, by which Wolbachia should operate to reduce DENV transmission in the field.     

Molecular cloning and characterization of double-stranded cDNA coding for bovine chymosin

A full-length cDNA copy of the mRNA encoding calf chymosin (also known as rennin), a proteolytic enzyme with commercial importance in the manufacture of cheese, has been cloned in an f1 bacteriophage vector. The nucleotide sequence of the cDNA was determined, and translation of that sequence into amino acids predicts that the zymogen prochymosin is actually synthesized in vivo as preprochymosin with a 16 amino acid signal peptide. In vitro translation of total poly(A)-enriched RNA from the calf fourth stomach (abomasum) and immunoprecipitation with antichymosin antiserum revealed that a form of chymosin (probably preprochymosin judging from the M_r-value) is the major in vitro translation product of RNA from that tissue. Gel-transfer hybridization of restriction endonuclease-cleaved bovine chromosomal DNA with labeled cDNA probes indicated that the two known forms of chymosin, A and B, must be products of two different alleles of a single chymosin gene.     

Therapy for Cancer of the Breast: Current Status of Steroid Hormone Receptors

Estrogen receptor (ER) assays in human breast cancer tissue have proved useful in selecting patients for endocrine therapies. The absence of ER indicates hormone independent tumors and precludes the use of endocrine therapy. Patients with positive tumor ER respond to endocrine therapy at nearly twice the rate of those patients chosen by clinical criteria, although about a third of ER positive tumors in patients still do not respond. Recently, research has been directed toward increasing the accuracy of the ER assay in the ER positive group. The absolute tumor ER value and the presence of progesterone receptor appear promising in this regard. The significance of nuclear estrogen receptor is being studied. Finally, the ER status of a primary breast tumor appears to be a marker for the length of time until recurrence after mastectomy, and for survival. The ER assay may prove valuable in planning new adjuvants in the treatment of breast cancer.     

Prenatal diagnosis for recessive dystrophic epidermolysis bullosa in 10 families by mutation and haplotype analysis in the type VII collagen gene (COL7A1).

BACKGROUND: Epidermolysis bullosa (EB) is a group of heritable diseases that manifest as blistering and erosions of the skin and mucous membranes. In the dystrophic forms of EB (DEB), the diagnostic hallmark is abnormalities in the anchoring fibrils, attachment structures beneath the cutaneous basement membrane zone. The major component of anchoring fibrils is type VII collagen, and DEB has been linked to the type VII collagen gene (COL7A1) at 3p21, with no evidence for locus heterogeneity. Due to life-threatening complications and significant long-term morbidity associated with the severe, mutilating form of recessive dystrophic EB (RDEB), there has been a demand for prenatal diagnosis from families with affected offspring. MATERIALS AND METHODS: Intragenic polymorphisms in COL7A1 and flanking microsatellite markers on chromosome 3p21, as well as detection of pathogenetic mutations in families, were used to perform PCR-based prenatal diagnosis from DNA obtained by chorionic villus sampling at 10-15 weeks or amniocentesis at 12-15 weeks gestation in 10 families at risk for recurrence of RDEB. RESULTS: In nine cases, the fetus was predicted to be normal or a clinically unaffected carrier of a mutation in one allele. These predictions have been validated in nine cases by the birth of a healthy child. In one case, an affected fetus was predicted, and the diagnosis was confirmed by fetal skin biopsy. CONCLUSIONS: DNA-based prenatal diagnosis of RDEB offers an early, expedient method of testing which will largely replace the previously available invasive fetal skin biopsy at 18-20 weeks gestation.