CTLA4 Autoimmunity-Associated Genotype Contributes to Severe Pulmonary Tuberculosis in an African Population

The gene of Cytotoxic T Lymphocyte-associated Antigen 4 (CTLA4), a negative regulator of T lymphocytes, contains a single-nucleotide polymorphism (SNP) at position +6230A->G (ct60A->G), which has been found associated with several autoimmune diseases and appears to reduce T-cell inhibitory activity. In Ghana, West Africa, we compared the frequencies of CTLA4 +6230 A/G and 6 haplotype-tagging SNPs in 2010 smear-positive, HIV-negative patients with pulmonary tuberculosis (TB) and 2346 controls matched for age, gender and ethnicity. We found no difference in allele frequencies between cases and controls. However, +6230A and a distinct CTLA4 haplotype and a diplotype comprising the +6230A allele were significantly less frequent among cases with large opacities in chest radiographs compared to those with small ones (P_{corrected [cor]} = 0.002, P_cor = 0.00045, P = 0.0005, respectively). This finding suggests that an increased T-cell activity associated with the CTLA4 +6230G allele contributes to pathology rather than to protection in pulmonary TB.     

Glycosylation of the phosphate binding protein, PstS, in Streptomyces coelicolor by a pathway that resembles protein O-mannosylation in eukaryotes

Previously mutations in a putative protein O -mannosyltransferase (SCO3154, Pmt) and a polyprenol phosphate mannose synthase (SCO1423, Ppm1) were found to cause resistance to phage, φC31, in the antibiotic producing bacteria Streptomyces coelicolor A3(2). It was proposed that these two enzymes were part of a protein O-glycosylation pathway that was necessary for synthesis of the phage receptor. Here we provide the evidence that Pmt and Ppm1 are indeed both required for protein O-glycosylation. The phosphate binding protein PstS was found to be glycosylated with a trihexose in the S. coelicolor parent strain, J1929, but not in the pmt ⁻ derivative, DT1025. Ppm1 was necessary for the transfer of mannose to endogenous polyprenol phosphate in membrane preparations of S. coelicolor . A mutation in ppm1 that conferred an E218V substitution in Ppm1 abolished mannose transfer and glycosylation of PstS. Mass spectrometry analysis of extracted lipids showed the presence of a glycosylated polyprenol phosphate (PP) containing nine repeated isoprenyl units (C₄₅-PP). S. coelicolor membranes were also able to catalyse the transfer of mannose to peptides derived from PstS, indicating that these could be targets for Pmt in vivo .     

The Mechanism of Supercoiled DNA Recognition by Eukaryotic Type I Topoisomerases: II. A Comparison of the Enzyme Interaction with Specific and Nonspecific Oligonucleotides

Data on the interaction of DNA type I topoisomerases from the murine and human placenta cells with specific and nonspecific oligonucleotides of various structures and lengths are summarized. The relative contributions of various contacts between the enzymes and DNA that have previously been detected by X-ray analysis to the total affinity of the topoisomerases for DNA substrates are estimated. Factors that determine the differences in the enzyme interactions with specific and nonspecific single- and double-stranded DNAs are revealed. The results of the X-ray analysis of human DNA topoisomerase I are interpreted taking into account data on the comprehensive thermodynamic and kinetic analysis of the enzyme interaction with the specific and nonspecific DNAs.     

The potential for and constraints on the evolution of compensatory ability in Asclepias syriaca

To investigate the potential for and constraints on the evolution of compensatory ability, we performed a greenhouse experiment using Asclepias syriaca in which foliar damage and soil nutrient concentration were manipulated. Under low nutrient conditions, significant genetic variation was detected for allocation patterns and for compensatory ability. Furthermore, resource allocation to storage was positively, genetically correlated both with compensatory ability and biomass when damaged, the last two being positively, genetically correlated with each other. Thus, in the low nutrient environment, compensatory ability via resource allocation to storage provided greater biomass when damaged. A negative genetic correlation between compensatory ability and plant biomass when undamaged suggests that this mechanism entailed an allocation cost, which would constrain the evolution of greater compensatory ability when nutrients are limited. Under high nutrient conditions, neither compensatory ability nor allocation patterns predicted biomass when damaged, even though genetic variation in compensatory ability existed. Instead, plant biomass when undamaged predicted biomass when damaged. The differences in outcomes between the two nutrient treatments highlight the importance of considering the possible range of environmental conditions that a genotype may experience. Furthermore, traits that conferred compensatory ability did not necessarily contribute to biomass when damaged, demonstrating that it is critical to examine both compensatory ability and biomass when damaged to determine whether selection by herbivores can favor the evolution of increased compensation. Received: 2 April 1999 / Accepted: 21 September 1999     

The who and why of pain: analysis by social class.

Physicians with an interest in pain have long suggested that the poor complain more and have a higher prevalence of neuroticism than do higher social groups. This assumption was tested by analysing the pain patterns in 500 consecutive patients attending a pain relief clinic. Results implied that scores for presenting pain, anxiety, and depression were similar to all social groups. After treatment scores for residual pain were significantly lower in all social classes, with greatest reduction in classes III, IV, and V. Almost identical results were obtained in a subgroup of patients with cancer but not in a subgroup with sciatica. That patients from the lower social classes have a higher perception of pain and are more neurotic than other group is a myth, probably resulting from poor communication between clinicians and patients of dissimilar socioeconomic class.     

Cultured astrocytes from a syncytium after maturation

The formation of functional gap junctions between astrocytes was investigated during differentiation of these cells in culture. Precursor cells of GFA (glial fibrillary acidic) protein-positive astrocytes were cultured in a chemically defined medium as a homogeneous population. These cells were rarely coupled to one neighbour, as revealed by electrical and dye coupling and never formed a large syncytium, as investigated by injection and spread of Lucifer Yellow. Differentiation with respect to GFA protein accumulation can be induced in these cells by culturing in horse serum-containing medium. The formation of functional junctions developed within 2 weeks in about 20% of the cells. Coupled cells formed a large syncytium. When the astrocytes were co-cultured with primary cerebellar cells (consisting predominantly of small neurons) after the switch to serum-containing medium the percentage of coupled astrocytes increased to about 65%. Again the coupled cells formed a large syncytium. Since no physical contact was possible between the astrocyte cultures and the primary cerebellar cells the stimulation of coupling had to be signalized by soluble factor(s).