Protective reaction of the myocardium in poisoning

Intensive synthesis of collagen-like substance was revealed in the rabbit myocardium during experimental diphtheria intoxication. It was more marked in the right ventricle 24 hours after the injection of diphtheria toxin. Since similar changes (the substance was mainly formed around blood vessels) have been observed in other cases of toxic myocardial alterations (i.e. ethanol intoxication, injection of pharmacological agents, etc.), it can be assumed that it is a standard protective reaction of the altered heart to the penetration of toxic agents from the blood into the myocardial tissue.     

Molecular Dynamics Simulations of PIP2 and PIP3 in Lipid Bilayers: Determination of Ring Orientation, and the Effects of Surface Roughness on a Poisson-Boltzmann Description

Molecular dynamics (MD) simulations of phosphatidylinositol (4,5)-bisphosphate (PIP₂) and phosphatidylinositol (3,4,5)-trisphosphate (PIP₃) in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers indicate that the inositol rings are tilted ∼40° with respect to the bilayer surface, as compared with 17° for the P-N vector of POPC. Multiple minima were obtained for the ring twist (analogous to roll for an airplane). The phosphates at position 1 of PIP₂ and PIP₃ are within an Ångström of the plane formed by the phosphates of POPC; lipids in the surrounding shell are depressed by 0.5-0.8 Å, but otherwise the phosphoinositides do not substantially perturb the bilayer. Finite size artifacts for ion distributions are apparent for systems of ∼26 waters/lipid, but, based on simulations with a fourfold increase of the aqueous phase, the phosphoinositide positions and orientations do not show significant size effects. Electrostatic potentials evaluated from Poisson-Boltzmann (PB) calculations show a strong dependence of potential height and ring orientation, with the maxima on the −25 mV surfaces (17.1 ± 0.1 Å for PIP₂ and 19.4 ± 0.3 Å for PIP₃) occurring near the most populated orientations from MD. These surfaces are well above the background height of 10 Å estimated for negatively charged cell membranes, as would be expected for lipids involved in cellular signaling. PB calculations on microscopically flat bilayers yield similar maxima as the MD-based (microscopically rough) systems, but show less fine structure and do not clearly indicate the most probable regions. Electrostatic free energies of interaction with pentalysine are also similar for the rough and flat systems. These results support the utility of a rigid/flat bilayer model for PB-based studies of PIP₂ and PIP₃ as long as the orientations are judiciously chosen.     

Fourth-derivative spectrophotometry of proteins

Fourth-derivative spectrophotometry offers several advantages over classical absorption or difference spectrophotometry in examining the characteristics of aromatic amino acids in proteins. The basic principles of the technique and its applications are outlined.     

Cellular regulation of ADP-ribosylation of proteins. III. Selective augmentation of in vitro ADP-ribosylation of histone H3 in murine thymic cells after in vivo emetine treatment

Thymic cells were isolated at intervals of between 0 and 144 h from mice that received one intraperitoneal injection of emetine (33 mg/kg), and thymus weight, incorporation of [14C]leucine into proteins and [3H]thymidine into DNA in intact thymic cells, as well as initial rates of protein ADP-ribosylation in permeabilized cells [A. Sóoki-Tóth, F. Asghari, E. Kirsten, and E. Kun (1987) Exp. Cell Res. 170, 93] were simultaneously monitored. The effect of emetine as an inhibitor of protein synthesis [F. Antoni, N. G. Luat, I. Csuka, I. Oláh, A. Sóoki-Tóth, and G. Bánfalvi (1987) Int. J. Immunopharmacol. 9, 333] corresponds to the induction of sequential cellular events, such as cell exit and remigration, by other antimitotic agents [C. Penit and F. Vasseur (1988) J. Immunol. 140, 3315] and produces an activation of proliferation of cells reentering into this organ. Proliferation, as demonstrated by a large increase in DNA synthesis and entrance into S phase, was kinetically related to an apparent increase in poly(ADP-ribose) polymerase activity in thymic cells and a highly significant in vitro ADP-ribosylation of histone H3. Since no DNA fragmentation occurred in thymic cells, as tested by a fluorometric technique [C. Birnboim and J. J. Jevac (1981) Cancer Res. 41, 1889], it is probable that a selective activation of poly(ADP-ribose) polymerase may have been induced in cells that undergo differentiation and proliferation while repopulating the thymus.     

The altered expression of MHC-class II determinants on monocytes of cancer patients

Summary The expression of MHC class II determinants Ia.7 (detected by cross reactive mouse anti-Ia^k antibody) and HLA-DR on monocytes (MO) of gastric and colorectal cancer patients was examined. An increased proportion of MO bearing the Ia.7 determinant was found, while the number of MO expressing DR was not elevated. In gastric cancer patients the increased expression of the Ia.7 determinant was most pronounced in advanced cancer (stage IVA and IVB). The increased expression of this determinant was related to the presence of the tumour as the number of MO expressing Ia.7 decreased 6 months following surgical resection of the tumour. Further, the increased expression of Ia.7 on MO correlated with the tumour infiltration of the serosa. The Ia.7 determinants were mainly expressed on MO which also expressed the receptor for the Fc part of immunoglobulin. Immunostaining in cellular infiltrates surrounding the tumour revealed that Ia.7⁺ macrophages (MØ) were more numerous than in normal gastric mucosa and severe chronic gastritis and were mostly present in close proximity to tumour cells, while DR⁺ MØ were mainly localized within the stromal tissue of the tumour and their number was not increased in cancer infiltrates. These observations indicate that the Ia.7⁺ subpopulation of MØ may be involved in the anti-tumour response of the host.     

Monoclonal antibodies against pertussis toxin subunits

Abstract Twenty monoclonal antibodies (mAbs) reacting with cholera toxin (CT) of Vibrio cholerae strain 569B were characterized in cross-section and G_M1 ganglioside inhibition assays. MAbs were characterized by reaction with CT and Escherichia coli heat-labile porcine strain (LT_p) and human strain (LTh) enterotoxins, and by G_M1 ganglioside inhibition of mAb binding. Eight of 10 CT-A specific and 3 of 10 CT-B-specific mAbs cross-reacted with LTh and LTp. G_M1 ganglioside inhibited reactions of the CT-B cross-reacting antibodies. Results showed that these epitodes common to the B subunit of CT and LT are located in or near the G_M1 ganglioside binding region, and that the G_M1 ganglioside-binding region of LT differs from that of CT.     

Cytoplasmic enzyme activities involved in energy and amino acid metabolism in pathological human renal cortex

Enzyme levels of lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (HBDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured in the cytosol of renal cortex samples from either normal and pathologic kidney tissue. The mean enzyme activity values, expressed in Units per gram of cytosolic protein decreased in the following order: normal cortex (LDH = 4,299 +/- 654; AST = 522 +/- 101; ALT = 197 +/- 44). chronic pyelonephritis (LDH = 2,360 +/- 876; AST = 297 +/- 117; ALT = 90 +/- 48), hydronephrosis (LDH = 2,208 +/- 1,264; AST = 279 +/- 165; ALT = 82 +/- 61), pyonephrosis (LDH = 1,410 +/- 596; AST = 158 +/- 69; ALT = 23.4 +/- 16.4) and renal tuberculosis (LDH = 1,149 +/- 481; AST = 93 +/- 34; ALT = 5.6 +/- 2.8). The decrease in the enzyme activities paralleled tissue damage and it was shown to affect cellular functionality in relation with energy and amino acid metabolism.     

Quantification of choline and ethanolamine phospholipids in rabbit myocardium

To facilitate evaluation of the influence of myocardial phospholipid metabolites on the development of electrophysiologic abnormalities induced by ischemia, a method for the quantification of choline and ethanolamine phospholipids suitable for accurate and reproducible analysis of small amounts of myocardium was developed. The procedure combines chloroform and methanol extraction of phospholipids after tissue homogenization with subsequent separation by sequential thin-layer and high-performance liquid chromatography. Phosphorus in purified lipid classes was determined with the correction for recovery based on 14C-labeled internal standards.     

Fine root turnover in forest ecosystems in relation to quantity and form of nitrogen availability: a comparison of two methods

Summary Two methods of estimating fine root production and turnover are compared for 13 forest ecosystems exhibiting a wide range in form (NH₄ ⁺ vs. NO₃ ^-) and quantity of available nitrogen. The two methods are by comparison of seasonal maxima and minima in biomess and by nitrogen budgeting. Both methods give similar results for stands with low rates of nitrification. The budgeting method predicts higher fine root turnover and productivity than the max-min method for systems with significant rates of nitrification.