Idiopathic CD4+ lymphocytopenia may be due to decreased bone marrow clonogenic capability

BACKGROUND: Idiopathic CD4+ lymphocytopenia is defined by a stable decrease of CD4+ T cells in the absence of any known cause of immune deficiency. The mechanisms responsible for the immunological impairment are still unknown, but a regenerative failure of hematopoietic stem/progenitor cells has been hypothesized. METHODS: We evaluated in the bone marrow (BM) of 5 patients with idiopathic CD4+ lymphocytopenia the phenotype of BM progenitor cells, their differentiation capacity with colony-forming cells and long-term culture-initiating cell assays, in parallel with the spontaneous IL-7 production in the patient sera. RESULTS: Compared with controls, a regenerative failure of hematopoietic stem cells has been observed, both in 'committed' and in 'uncommitted' progenitor cells, despite high IL-7 serum levels. The percentage of phenotypically primitive CD34+CD38-DR+ cells (this includes the lymphoid precursor cells) was decreased, suggesting an involvement of the more primitive BM compartment in the de novo T cell generation. CONCLUSIONS: Despite the low number of patients, due to the low incidence of the disease, the decrease of primitive precursors sustains the possibility that diminished stem cell precursors might contribute to the development of CD4+ T cell depletion.     

Prevalence of transmitted HIV-1 drug resistance and the role of resistance algorithms: data from seroconverters in the CASCADE collaboration from 1987 to 2003

OBJECTIVES: To examine factors influencing the rate of transmitted drug resistance (TDR) among seroconverters, with particular emphasis on 3 widely used genotypic drug resistance algorithms. METHODS: The study used data from CASCADE (Concerted Action on Seroconversion to AIDS and Death in Europe), a collaboration of seroconverter cohorts in Europe and Canada. Genotypic resistance data were derived within 18 months of the last seronegative test or date of laboratory evidence of acute infection and before the initiation of antiretroviral therapy. The Stanford algorithm was used to analyze each individual's nucleotide sequence. A multivariate logistic model was used to assess independent relationships between the presence of TDR and exposure category, sex, age at seroconversion, and year of seroconversion. The paper also describes 3 alternative definitions of resistance: the Stanford algorithm, the key resistance mutations defined by the International AIDS Society, and the Agence Nationale de Recherches sur le Sida (ANRS) algorithm. RESULTS: Forty-five of 438 patients (10.3%) seroconverting between 1987 and 2003 were infected with a drug-resistant HIV-1 variant. Forty patients (9.1%) showed resistance mutations to only 1 class of antiretroviral drugs, 2 (0.5%) to 2 classes, and 3 (0.7%) to 3 classes of antiretroviral therapy. It was suggested that individuals seroconverting later in calendar time were more likely to have TDR (relative risk 3.89 and 95% CI: 0.84 to 18.02, and relative risk 4.69 and 95% CI: 1.03 to 21.31, for 1996-1999 and 2000-2003, respectively, compared with pre-1996; P trend = 0.08). This trend was apparent regardless of the definition of TDR used. The total estimated proportion of individuals with TDR varied between 10.3% and 15.5% according to which definition was used. CONCLUSIONS: Evidence was found for the rise of TDR over time. A specific definition of what constitutes TDR rather than a simple list of mutations is needed.     

Parasite-susceptibility phenotypes of F1 Biomphalaria glabrataprogeny derived from interbreeding Schistosoma mansoni-resistant and -susceptible snails

In an effort to investigate the 'flow' of parasite-resistance genes through laboratory snail populations, we determined the susceptibility of progeny snails from freely interbreeding parasite-susceptible and parasite-resistant parents. Five parental populations of Biomphalaria glabrata were used to generate the progeny snails. Three of them contained different proportions of Schistosoma mansoni-susceptible albino snails (NMRI stock) and S. mansoni-resistant pigmented snails (BS-90), while single stock controls comprised the other two parental populations. F(1) snails from each parental population were exposed to S. mansoni miracidia. Some of the progeny snails were exposed as juveniles, others as adults. According to Hardy-Weinberg principle predictions, the F(1) generation from the three pigmented/albino parental populations displayed higher than expected numbers of pigmented (resistant) snails and lower than expected numbers of albino (susceptible) snails. Among the assumptions of the Hardy-Weinberg principle that were not met within these populations could include non-random mating, unequal fecundity, different hatching and survival rates of different genotypes, or other life-history differences between snail stocks. It is clear, though, that for these two laboratory snail stocks there is no fitness cost attached to genetic resistance to the parasite.     

Human X-chromosomal lineages in Europe reveal Middle Eastern and Asiatic contacts

Within Europe, classical genetic markers, nuclear autosomal and Y-chromosome DNA polymorphisms display an east-west frequency gradient. This has been taken as evidence for the westward migration of Neolithic farmers from the Middle East. In contrast, most studies of mtDNA variation in Europe and the Middle East have not revealed clinal distributions. Here we report an analysis of dys44 haplotypes, consisting of 35 polymorphisms on an 8 kb segment of the dystrophin gene on Xp21, in a sample of 1203 Eurasian chromosomes. Our results do not show a significant genetic structure in Europe, though when Middle Eastern samples are included a very low but significant genetic structure, rooted in Middle Eastern heterogeneity, is observed. This structure was not correlated to either geography or language, indicating that neither of these factors are a barrier to gene flow within Europe and/or the Middle East. Spatial autocorrelation analysis did not show clinal variation from the Middle East to Europe, though an underlying and ancient east-west cline across the Eurasian continent was detected. Clines provide a strong signal of ancient major population migration(s), and we suggest that the observed cline likely resulted from an ancient, bifurcating migration out of Africa that influenced the colonizing of Europe, Asia and the Americas. Our study reveals that, in addition to settlements from the Near East, Europe has been influenced by other major population movements, such as expansion(s) from Asia, as well as by recent gene flow from within Europe and the Middle East.     

Polyamine N-acetyltransferase in Leishmania amazonensis

 N-Acetyltransferase, which is suggested to be responsible for the production of N ¹-acetylspermidine in Leishmania amazonensis and to be involved in the process of inactivation and degradation of excessive polyamines, was partially purified and characterized. Among the substrates tested, sym-norspermidine, sym-norspermine, and 1,3-diaminopropane had the highest reaction rates, but the naturally occurring polyamines spermine and spermidine were also acetylated at considerable rates, whereas putrescine was a poor substrate. The Michaelis constants (K _m values) for spermine and spermidine were 0.66 and 3.3 mM, respectively. The K_m value for acetylcoenzyme A (acetyl-CoA) was determined to be 34 μM. CoA inhibited the reaction in a competitive manner; the inhibition constant was 5 μM. The enzyme showed an apparent relative molecular mass of 35,000. Received: 16 November 1995 / Accepted: 10 January 1996     

Detection of DNA damage after hyperbaric oxygen (HBO) therapy

Hyperbaric oxygen HBO therapy is successfully used for the treatmentof a variety of conditions. However, exposure to high concentrationsof oxygen is known to induce damage to cells, possibly due toan increased oxygen radical production. As reactive oxygen speciesalso cause DNA damage, we investigated the DNA-damaging effectof HBO with the alkaline version of the single cell gel testcomet assay. Oxidative DNA base modifications were determinedby converting oxidized DNA bases to strand breaks using bacterialformamidopyrimidine-DNA glycosylase FPG, a DNA repair enzyme,which specifically nicks DNA at sites of 8-oxo-guanines andformamidopyrimidines. HBO treatment under therapeutic conditionsclearly and reproducibly induced DNA damage in leukocytes ofall test subjects investigated. Increased DNA damage was foundimmediately at the end of the treatment, while 24 h later, noeffect was found. Using FPG protein we detected significantoxidative base damage after HBO treatment DNA damage was detectedonly after the first treatment and not after further treatmentsunder the same conditions, indicating an increase in antioxidantdefences. DNA damage did not occur when the HBO treatment wasstarted with a reduced treatment time which was then increasedstepwise. ³To whom correspondence should be addressed     

The myogenic response in isolated rat cerebrovascular arteries: vessel model

We develop an integrated model of isolated rat arterial resistance vessel (RV), which can simulate its major property of myogenic response. The vascular smooth muscle cell is an important component of the wall of this vessel, and serves as a vasomotor organ providing the active tension generation that underlies the myogenic response of the wall to stretch. In the previous study, we focused on the development of a smooth muscle cell model that can mimic the strain-sensing and force-generating features of the myogenic mechanism. In the current model, we embed this cell model in a larger vessel wall configuration, and couple the time course of cellular contractile activation to macroscopic changes in vessel diameter. The integrated model is used to mimic published pressure-vessel diameter data obtained from isolated RVs that are mounted in a hydraulic test apparatus. The model provides biophysically based insights into the myogenic mechanism as it responds to changes in transmural pressure, in the presence and absence of Ca2+ blockers applied to the bathing fluid.It mimics measured data very well and provides a model that is able to link events at subcellular level to macroscopic changes in vessel diameter. The model initiates a mechanistic approach to investigate myogenic response, which has not been taken previously by any other models.