Change in neutrophils in liquidators of the consequences of the accident at the Chernobyl Atomic Electric Power Station

In result of own researches and analysis of the literature? the information about high sensitivity of neutrophils of peripheric blood to infringements of constancy of internal state of body, arising as reply to radiating influence, are received. Ionized radiation modulates greatly properties and functions of neutrophilic granulocytes, which are the most sensitive and high-modulated cells of non-specific resistance system. The changes of the functional-metabolic status of neutrophils in participants of liquidation of consequences of Chernobyl disaster have been saving during 10 years after influence of the extreme, including radiating, factors of failure.     

Acquired heart valve pathology. An update for the millennium

Two inflammatory vascular diseases often show multinucleated macrophages: Takayasu's disease and Horton's disease. Takayasu's disease is a segmentary panarteritis most prominent in the adventitia. Lesions show an inflammatory infiltrate close to the external elastic lamina. Progressive stenosis of the artery, sometimes complicated by calcifying atheroma is the typical course. Horton's disease or temporal arteritis is another segmentary arteritis. Lesions show a mixed inflammatory infiltrate partly localized in the adventitia where there are T CD4+ lymphocytes secreting II-2 and IFN-gamma and also macrophages expressing TGF beta 1, IL-6 and IL-1 beta, and partly situated in the interior part of the wall, around the internal elastic lamina, and mostly made of macrophages and giant cells which produce TNF, collagenase and nitric oxide that are responsible for destruction of the wall. The variety and subtleness of some lesions do not always make a precise diagnosis possible. But any inflammatory vascular lesion, even slight, can reveal a systemic vasculitis.     

Phosphorylation of photolyzed rhodopsin is calcium-insensitive in retina permeabilized by alpha-toxin

Light triggers the phototransduction cascade by activating the visual pigment rhodopsin (Rho --> Rho*). Phosphorylation of Rho* by rhodopsin kinase (RK) is necessary for the fast recovery of sensitivity after intense illumination. Ca2+ ions, acting through Ca2+-binding proteins, have been implicated in the desensitization of phototransduction. One such protein, recoverin, has been proposed to regulate RK activity contributing to adaptation to background illumination in retinal photoreceptor cells. In this report, we describe an in vitro assay system using isolated retinas that is well suited for a variety of biochemical assays, including assessing Ca2+ effects on Rho* phosphorylation. Pieces of bovine retina with intact rod outer segments were treated with pore-forming staphylococcal alpha-toxin, including an alpha-toxin mutant that forms pores whose permeability is modulated by Zn2+. The pores formed through the plasma membranes of rod cells permit the diffusion of small molecules <2 kDa but prevent the loss of proteins, including recoverin (25 kDa). The selective permeability of these pores was confirmed by using the small intracellular tracer N-(2-aminoethyl) biotinamide hydrochloride. Application of [gamma-32P]ATP to alpha-toxin-treated, isolated retina allowed us to monitor and quantify phosphorylation of Rho*. Under various experimental conditions, including low and high [Ca2+]free, the same level of Rho* phosphorylation was measured. No differences were observed between low and high [Ca2+]free conditions, even when rods were loaded with ATP and the pores were closed by Zn2+. These results suggest that under physiological conditions, Rho* phosphorylation is insensitive to regulation by Ca2+ and Ca2+-binding proteins, including recoverin.     

Biological characterization of Rev variation in equine infectious anemia virus

Sequence analysis identified significant variation in the second exon of equine infectious anemia virus (EIAV) rev. Functional analysis indicated that limited amino acid variation in Rev significantly altered the export activity of the protein but did not affect Rev-dependent alternative splicing. EIAV Rev can mediate export through two independent cis-acting Rev-responsive elements (RREs), and differences among Rev variants were more pronounced when both RREs were present. Variation in Rev may be an important mechanism for regulation of virus replication in vivo and may contribute to changes in clinical disease.     

3-Pyridylethanolamines: potent and selective human beta 3 adrenergic receptor agonists

The 3-pyridylethanolamine L-757,793 is a potent beta 3 AR agonist (EC50 6.3 nM, 70% activation) with 1,300- and 500-fold selectivity over binding to the beta 1 and beta 2 ARs, respectively. L-757,793 stimulated lipolysis in rhesus monkeys (ED50 0.2 mg/kg) with a maximum response equivalent to that elicited by isoproterenol.     

Sequence analysis of an 80 kb human neocentromere

We previously described the cloning of an 80 kb DNA corresponding to the core protein-binding domain of a human chromosome 10-derived neocentromere. Here we report the complete sequence of this DNA (designated NC DNA) and its detailed structural analysis. The sequence is devoid of human centromeric alpha-satellite DNA and the pericentric beta- and gamma-satellites, the ATRS and 48 bp repeat DNA. One copy of a sequence that is related to the CENPB box motif is present, and a number of copies of other pericentric sequences including pJalpha and classical satellites I and III are present but both their relative sparsity and non-tandem organization suggest that each sequence, on its own, is unlikely to mimic any role the sequence may have in the normal centromere. The DNA-binding motifs of the architectural and regulatory proteins HMGI and topoII have a normal abundance and random distribution, implying that these sequences are not key functional elements. The total A + T content of the sequence is not notably different from that of the human genome, but an abundance of AT-rich islands and a biased distribution of these islands within the NC sequence are clearlydiscernible and may be functionally significant. Substantial amounts of transposable elements and low copy number tandem repeats, including several that are highly AT- and purine-rich, are also present and may act as functional elements. One of the AT-rich tandemrepeats (AT28) may form interesting structures and is described in detail. The defined features show only a loose resemblance to the structures of known centromeres, highlighting the possibility that, rather than a conserved primary sequence, it is the overallcomposition and distribution patterns of various unknown functional elements, or any 'ordinary' DNA under appropriate epigenetic influences, that determine centromere formation and function. This is the firstdetailed analysis of a neocentromere DNA and provides a basis for comparison against future sequences.     

The role of prevention in workers' compensation managed care arrangements

Managed care's emphasis on restricting costs may interfere with its ability to assume a prevention orientation. The authors present models, derived from group health and workers' compensation, of successful incorporation of prevention into managed care arrangements.     

Isolation of human O6-alkylguanine-DNA alkyltransferase mutants highly resistant to inactivation by O6-benzylguanine

The activity of O6-alkylguanine-DNA alkyltransferase (AGT) protects cells from killing by methylating or chloroethylating agents. AGT is strongly inhibited by O6-benzylguanine (ED50, 0.2 microM), and this drug is presently undergoing clinical trials to enhance chemotherapy by alkylating agents. Point mutations such as P140A (ED50, 5 microM) render AGT resistant to O6-benzylguanine (BG). Selection for such mutants may prove to be a problem in the use of BG, and a better knowledge of the factors underlying resistance to BG will enable the rational design of improved inhibitors able to inactivate these mutants. BG-resistant AGT mutants may also be valuable for expression in bone marrow stem cells to reduce myelosuppression brought about by alkylating agents, to increase the therapeutic index of therapies including BG, and for use as a selectable marker to allow other genes to be expressed in such stem cells. We have therefore set up a general screen to obtain such mutants by using the ability of AGT to protect Escherichia coli GWR109 lacking endogenous AGT from killing by N-methyl-N'-nitro-N-nitrosoguanidine. When the cells were rendered permeable to BG by mutating the lipopolysaccharide membrane component forming strain TRG8, the protection by AGT expression was abolished by treating the cells with BG. The known P140A mutant was used to test the system and was highly selected for by treatment with 50 microM BG and 40 microg/ml N-methyl-N'-nitro-N-nitrosoguanidine. The sequence coding for PVP at positions 138-140 in AGT was replaced with a random nucleotide sequence, and this library was used to transform TRG8. All of the 59 colonies analyzed having AGT activity that survived the selection from the pool of 36,000 transformants were resistant to BG. Many (69%) of these mutants contained lysine at position 140, and all of these showed the highest level of resistance with <10% loss of activity when crude cell extracts were incubated with 1.2 mM BG. This result was confirmed with three mutants (P138K/V139L/P140K, P138M/V139L/P140K, and P140K), which were purified to homogeneity. The next most common residues found at position 140 were arginine (7%) and asparagine (7%). Studies carried out with purified preparations of mutants P140R and P140N revealed that these mutations also provided resistance to BG but to a lesser extent than P140K (ED50s of 190 and 7 microM, respectively). These results indicate that: (a) this screening method can be used to evaluate BG resistance of single or multiple changes throughout the AGT sequence; and (b) replacement of proline-140 with lysine is the most effective point mutation at this site causing BG resistance and is more than 200 times more effective than replacement with alanine.     

A 1.4 A crystal structure for the hypoxanthine phosphoribosyltransferase of Trypanosoma cruzi

The hypoxanthine phosphoribosyltransferase (HPRT) from Trypanosoma cruzi, etiologic agent of Chagas' disease, was cocrystallized with the inosine analogue Formycin B (FmB) and the structure determined to 1.4 A resolution. This is the highest resolution structure yet reported for a phosphoribosyltransferase (PRT), and the asymmetric unit of the crystal contains a dimer of closely associated, nearly identical subunits. A conserved nonproline cis peptide in one active-site loop exposes the main-chain nitrogen to the enzyme active site, while the adjacent lysine side chain interacts with the other subunit of the dimer, thereby providing a possible mechanism for communication between the subunits and their active sites. The three-dimensional coordinates for the invariant Ser103-Tyr104 dipeptide are reported here for the first time. These are the only highly conserved residues in a second active-site loop, termed the long flexible loop, which is predicted to close over the active site of HPRTs to protect a labile transition state [Eads et al. (1994) Cell 78, 325-334]. This structure represents a major step forward in efforts to design/discover potent selective inhibitors of the HPRT of T. cruzi.