Tumor necrosis factor-alpha priming of phospholipase A2 activation in human neutrophils. An alternative mechanism of priming.

The cytokine, TNF-alpha, interacts with human neutrophils (PMN) via specific membrane receptors and primes leukotriene B4 (LTB4) production in PMN for subsequent stimulation by calcium ionophores. We have further examined the effects of TNF-alpha on arachidonic acid (AA) release, LTB4 production, and platelet-activating factor (PAF) formation in PMN by prelabeling cells with either [3H]AA or [3H]lyso-PAF, priming with human rTNF-alpha, and then stimulating with the chemotactic peptide, FMLP. TNF-alpha, alone, had little effect; minimal AA release, LTB4 or PAF production occurred after PMN were incubated with 0 to 1000 U/ml TNF-alpha. However, when PMN were first preincubated with 100 U/ml TNF-alpha for 30 min and subsequently challenged with 1 microM FMLP, both [3H] AA release and LTB4 production were elevated two- to threefold over control values. Measurement of AA mass by gas chromatography and LTB4 production by RIA confirmed the radiolabeled results. TNF-alpha priming also increased PAF formation after FMLP stimulation. These results demonstrate that TNF-alpha priming before stimulation with a physiologic agonist can enhance activation of phospholipase A2 (PLA2) resulting in increased AA release and can facilitate the activities of 5-lipoxygenase (LTB4 production) and acetyltransferase (PAF formation). Reports in the literature have hypothesized that the priming mechanism involves either production of PLA2 metabolites, increased diglyceride (DG) levels, or enhanced cytosolic calcium levels induced by the priming agent. We investigated these possibilities in TNF-alpha priming of PMN and report that TNF-alpha had no direct effect on PLA2 activation or metabolite formation. Treatment of PMN with TNF-alpha did not induce DG formation and, in the absence of cytochalasin B, no increased DG production (measured by both radiolabel techniques and mass determinations) occurred after TNF-alpha priming followed by FMLP stimulation. TNF-alpha also had no effect on basal cytosolic calcium and did not enhance intracellular calcium levels after FMLP stimulation. These results suggest that an alternative, as yet undefined, mechanism is active in TNF-alpha priming of human PMN.     

Thymic irradiation inhibits the rapid recovery of TH1 but not TH2-like functions of CD4+ T cells after total lymphoid irradiation.

Four to six weeks after total lymphoid irradiation (TLI), there is a selective deficit in the CD4+ T cells which secrete IL-2, proliferate in the MLR, and induce GVHD (Th1-like functions). A similar deficit in CD4+ T cells which secrete IL-4 and help antibody responses (Th2-like functions) is not observed. In the present study, shielding of the thymus with lead during TLI increased the Th1-like functions of CD4+ cells. Mice without thymus shields showed a marked selective reduction in the medullary stromal cells identified with the monoclonal antibody, MD1, and the severe reduction was prevented with thymus shields. Thus, shielding the thymus prevents the depletion of thymic medullary stromal cells and allows for a rapid recovery of Th1-like functions in the mouse spleen after TLI. Th2-like functions recover rapidly after TLI whether or not the thymus is irradiated.     

Effect of benzyl alcohol on phospholipid transverse mobility in human erythrocyte membrane.

The effect of benzyl alcohol on the transverse mobility and repartition of phospholipids in the human erythrocyte membrane was investigated using electron spin resonance and morphological modification of red blood cells. Transmembrane internalization rates and equilibrium distribution in red blood cells of short-chain spin-labeled phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine were strongly modified by treatment with 10-70 mM benzyl alcohol. A dual effect was observed: (a) at 4 degrees C and 37 degrees C there was an N-ethylmaleimide-sensitive, long lasting and fully reversible increase in the spin-labeled phosphatidylserine and phosphatidylethanolamine internalization rate; (b) at 37 degrees C, an enhancement of N-ethylmaleimide-insensitive fluxes of all the labeled phospholipids through the membrane occurred. Both effects were dose-dependent. Erythrocytes submitted to benzyl alcohol incubation also showed dose-dependent shape changes: an immediate one from discocytes to echinocytes, followed by a slower N-ethylmaleimide- and ATP-dependent change to stomatocytes. Moreover, benzyl alcohol treatment was shown to lead to enhanced hydrolysis of intracellular ATP. All the effects of benzyl alcohol can be described as an accumulation of labeled phosphatidylethanolamine (and labeled phosphatidylcholine at 37 degrees C) in the inner leaflet. This can be interpreted as a perturbation of the erythrocyte membrane, leading to an energy-consuming specific increase in aminophospholipid translocase activity, in addition to a slow and passive bidirectional flux of all phospholipids at 37 degrees C.     

Hoppel-family of mobile elements of Drosophila melanogaster, flanked by short inverted repeats and having preferential localization in the heterochromatin regions of the genome

A mobile element (ME) having 91% homology with Dm1360 (Kholodilov et al., 1987) has been cloned from the Drosophila melanogaster genome and sequenced. The family of ME was designated hoppel. The members of this family are flanked by short inverted repeats likewise P, hobo and HB. The hoppel is hybridized with 10-30 euchromatic sites of polytene chromosomes of different Drosophila stocks. Abundant hybridization with heterochromatic regions of chromosomes-chromocenter, pericentric heterochromatin, the 4 chromosome and telomeres was observed in all stocks of D. melanogaster examined and in D. simulans. At least six genomic variants of ME differing in length of the central part were revealed. Hoppel possesses ARS activity similar to the P element. Two ME hoppel were shown to be arranged as a direct repeat in the recombinant phage.     

Lipoxygenbase-derived products of arachidonic acid mediate stimulation of hexose uptake in human polymorphonuclear leukocytes

The titration of metal-freed bovine α-lactalbumin with Mg²⁺ ions causes a two-stepped decrease in the tryptophan fluorescence quantum yield and a pronounced spectral shift towards shorter wavelengths, which seems to be a result of the binding of two magnesium ions to the protein molecule. The magnesium binding constants evaluated from the fluorimetric Mg²⁺-titration are 2·10³ and 2·10² M^?1. Mg²⁺ ions in millimolar concentrations almost do not influence the binding of Ca²⁺ ions to the protein.     

A 45,XX,-5,-14,+t(5q;14q)mat cri du chat child.

A two-year-old girl has the following features of the cri du chat syndrome: microcephaly, hypertelorism, downward slanting of the palpebral fissures, psychomotor retardation and a cat-like cry. She is only of five patients having the cat cry syndrome with 45 chromosomes. Her karyotype is 45,XX, -5, -14, +t(5; 14)(5qter leads to 5p11: : 14q11 leads to 14qter) with the translocation inherited from her mother and maternal grandmother, each of whom is the carrier of a balanced translocation 46,XX,t(5;14)(p11q11). Normal plasma activity for hexosaminidase B suggests the locus for this enzyme is not located in the delected segment of 5 p.     

A new species of Metacnephia Crosskey (Diptera: Simuliidae) from the south of England,with notes on its habitat and biology

Since the report of (Simulium) tredecimatum from “the stomach of a trout, England” no specimens of the genus Metacnephia have been reported from the British Isles. A full account of the morphological features of the larvae, pupae and adults of a new species, Metacnephia amphora is given together with a brief account of its larval growth and presence on a wide range of substrata in a small, temporary stream.     

Activity of some enzymes of energy metabolism in striated muscle of obese subjects with respect to body composition.

The effect of obesity on the activity of some enzymes of energy supplying metabolism was studied in male and female groups of different body weight, using tissue samples of m. quadriceps femoris obtained by a biopsy needle. Both obese males and females displayed a distinct tendency towards anaerobic metabolism (high lactate dehydrogenase activities). The assumption that cytoplasm has an increased capacity in the muscle of the obese for reduction syntheses is supported by the increased ratio of malate dehydrogenase to citrate synthase activities. Compared with controls, less activity of enzymes associated with fatty acid and glucose degradation (hexokinase, hydroxyacyl-CoA dehydrogenase, citrate synthase) was observed in obese males. In obese females the latter enzyme activities did not differ from those in the controls; however, lactate dehydrogenase and triosophosphate dehydrogenase activities were significantly higher. Significant inverse correlations between hexokinase and hydroxyacyl- CoA dehydrogenase activities, on the one hand, and indicators of body composition and body weight, on the other, were found in males. The female group did not display analogous significant relations between the enzymatic organization and indicators of body composition.     

Studies on Ephemerella ignita (Poda) in a chalk stream in Southern England

The nymphs ofEphemerella ignita occurred in all months except October in the Bere Stream at Bere Heath, a small chalk stream in Southern England. Peak densities of 1,498 m^–2 and 753 m^–2 were recorded in May by two sampling methods used simultaneously. The seasonal patterns of growth and abundance are compared with the findings of other authors. A maximum biomass of 0.82 g m^–2 preserved dry weight is compared with figures for two of the most common invertebrate groups present; the Simuliidae and Oligochaeta.