Restriction map of a 35-kb HLA fragment constructed by nested deletion 'drop-out' mapping

An efficient method for generating detailed restriction maps of large cloned DNA segments is demonstrated. The mapping strategy entails comparing restriction fragments from a parent clone and from nested deletion derivatives of that clone. In a set of deletion plasmids of decreasing size, an individual fragment will be lost, or 'drop-out', according to its position in the cloned fragment. In this demonstration, nested deletions were generated in both directions in a 35-kb DNA segment from the human leukocyte antigen (HLA) region by intramolecular transposition of an engineered gamma delta (Tn1000) element present in a special 'deletion factory' cloning vector [Wang et al., Proc. Natl. Acad. Sci. USA 90 (1993) 7874-7878]. Fifteen plasmids with deletions extending in one direction and eleven plasmids with deletions extending in the opposite direction were digested singly by each of four restriction enzymes. A total of 36 cleavage sites were mapped in the 35-kb HLA fragment. This drop-out approach using nested deletions provides a simple and efficient means of mapping restriction sites, genes and other features of interest in cosmid-sized cloned DNA segments or DNAs.     

Hydrocarbons and porphyrins in rock extracts

Specimens of rock extracts from the vicinity of oil deposits in the Persian Gulf area were analysed. Chromatographic methods were used to separate the individual (structurally or chemically related) groups. The most substantial difference between the rock extracts and high-boiling petroleum fractions is in the relatively high content of porphyrins and high-molecular polar substances. All groups of compounds (saturated and aromatic hydrocarbon fractions, polar substances, porphyrins) were characterized in detail, using suitable methods of instrumental analysis.     

The electrochemical properties of cadmium forms of zeolite of type A

The electrochemical behaviour of pressed cadmium forms of zeolite of type A was investigated by various electrochemical methods. It is shown that the behaviour is typical of electrolytic systems but also with anodic and cathodic passivation of platinum electrodes. The electrode processes and the mechanism of charge transport through the electrolyte and the layer adjacent to the electrode are consisdered.     

RRK model of unimolecular surface reaction

After the chemisorption of a polyatomic molecule on an active site of a catalyst, the adsorption energy is localized in the new, molecule-active site bond. Assuming the free flow of adsorption energy into the internal vibrations of the adsorbed molecules only, the Rice-Ramsperger-Kassel (RRK) statistical theory of a spontaneous decomposition can describe the surface reaction of these molecules. The mean vibrational energy of adsorbed molecules is determined by the temperature of reactants in the gas phase, and by the heat of adsorption.     

Infection with human immunodeficiency virus type 1 upregulates DNA methyltransferase, resulting in de novo methylation of the gamma interferon (IFN-gamma) promoter and subsequent downregulation of IFN-gamma production

The immune response to pathogens is regulated by a delicate balance of cytokines. The dysregulation of cytokine gene expression, including interleukin-12, tumor necrosis factor alpha, and gamma interferon (IFN-gamma), following human retrovirus infection is well documented. One process by which such gene expression may be modulated is altered DNA methylation. In subsets of T-helper cells, the expression of IFN-gamma, a cytokine important to the immune response to viral infection, is regulated in part by DNA methylation such that mRNA expression inversely correlates with the methylation status of the promoter. Of the many possible genes whose methylation status could be affected by viral infection, we examined the IFN-gamma gene as a candidate. We show here that acute infection of cells with human immunodeficiency virus type 1 (HIV-1) results in (i) increased DNA methyltransferase expression and activity, (ii) an overall increase in methylation of DNA in infected cells, and (iii) the de novo methylation of a CpG dinucleotide in the IFN-gamma gene promoter, resulting in the subsequent downregulation of expression of this cytokine. The introduction of an antisense methyltransferase construct into lymphoid cells resulted in markedly decreased methyltransferase expression, hypomethylation throughout the IFN-gamma gene, and increased IFN-gamma production, demonstrating a direct link between methyltransferase and IFN-gamma gene expression. The ability of increased DNA methyltransferase activity to downregulate the expression of genes like the IFN-gamma gene may be one of the mechanisms for dysfunction of T cells in HIV-1-infected individuals.     

Interfacial properties of self-reinforced composite poly(methyl methacrylate)

The authors describe ten years of experience in breast reconstruction in the Department of Plastic and Reconstructive Surgery in the District Hospital of Santarém--Portugal. Ninety-nine patients were treated with 106 reconstructions, most of these were immediate and some were delayed. The authors were interested in providing an adequate volume, but also into obtaining an acceptable aesthetic result. This contributes considerably to the psychological recovery of the patients.     

Depression of cardiac function after deep hypothermic circulatory arrest in deeply anesthetized neonatal lambs

Cardiac dysfunction is common after neonatal cardiac operations. Previous in vivo studies in neonatal animal models however, have failed to demonstrate decreased left ventricular function after ischemia and reperfusion. Cardiac dysfunction may have been masked in these studies by increased endogenous catecholamine levels associated with the use of light halothane anesthesia. Currently, neonatal cardiac operations are often performed with deep opiate anesthesia, which suppresses catecholamine surges and may affect functional recovery. We therefore examined the recovery of left ventricular function after ischemia and reperfusion in neonatal lambs anesthetized with high-dose fentanyl citrate (450 micrograms/kg administered intravenously). Seven intact neonatal lambs with open-chest preparation were instrumented with left atrial and left ventricular pressure transducers, left ventricular dimension crystals, and a flow transducer. The lambs were cooled (< 18 degrees C) on cardiopulmonary bypass (22 +/- 6 minutes), exposed to deep hypothermic circulatory arrest (46 +/- 1 minutes), and rewarmed on cardiopulmonary bypass (30 +/- 10 minutes). Catecholamine levels and indexes of left ventricular function were determined before (baseline) and 30, 60, 120, 180, and 240 minutes after termination of cardiopulmonary bypass. Levels of epinephrine, norepinephrine, and dopamine were unchanged from baseline values. Left ventricular contractility (slope of end-systolic pressure-volume relationship) was depressed from baseline value (31.7 +/- 9.3 mm Hg/ml) at 30 minutes (15.7 +/- 6.4 mm Hg/ml) and 240 minutes (22.7 +/- 6.4 mm Hg/ml) but unchanged between 60 and 180 minutes. Left ventricular relaxation (time constant of isovolumic relaxation) was prolonged from baseline value (19.0 +/- 3.0 msec) at 30 minutes (31.4 +/- 10.0 msec) and 240 minutes (22.1 +/- 2.8 msec) but unchanged between 60 and 180 minutes. Afterload (left ventricular end-systolic meridional wall stress) was decreased at 30, 60, and 240 minutes. Indexes of global cardiac function (cardiac output, stroke volume), preload (end-diastolic volume), and left ventricular compliance (elastic constant of end-diastolic pressure-volume relationship) were unchanged from baseline values. In deeply anesthetized neonatal lambs exposed to ischemia and reperfusion, left ventricular contractility, relaxation, and afterload are markedly but transiently depressed early after reperfusion and mildly depressed late after reperfusion.     

Isolation from human placenta of the IgG transporter, FcRn, and localization to the syncytiotrophoblast: implications for maternal-fetal antibody transport

The IgG transporter responsible for ferrying maternal IgG across the human placenta to fetal circulation has not been identified, although the human homologue of the neonatal rat Fc receptor (FcRn), a heterodimer with pH-dependent IgG affinity, structurally similar to MHC Class I molecules, was recently proposed as a candidate. Affirming this hypothesis, we describe herein the specific copurification from human placenta of 46- and 14-kDa proteins by IgG affinity at acid pH. The larger protein, characterized by its amino acid sequence and by immunoblot, is the alpha-chain of human FcRn (hFcRn). The smaller is beta2-microglobulin. Their coisolation by ligand affinity suggests that they comprise the hFcRn heterodimer. Placenta sections stained immunohistochemically with anti-hFcRn alpha-chain peptide Abs show extensive expression of hFcRn in the syncytiotrophoblast and traces in the endothelium and other unidentified cells of the villus stroma. We find alpha-chain mRNA by Northern analysis in human placenta and in human trophoblast-like cell lines (JEG-3, ED27) but not in a human myelocytic cell line (HL60). We suggest that the placental hFcRn heterodimer may transport IgG to the fetus by a mechanism in which maternal IgG is pinocytosed nonspecifically and then carried to fetal tissues by a pH gradient from acidic endosomes to the pH-neutral basolateral surface of the syncytiotrophoblast. Furthermore, the known characteristics of FcRn suggest a wider function, that it is the receptor postulated by Brambell in the 1960s to regulate tissue and serum IgG concentrations by controlling IgG transport and catabolism.