Evidence that the effect of physical exercise on NK cell activity is mediated by epinephrine

The present study was designed to test the hypothesis that the changes in natural killer (NK) cell activity in response to physical exercise were mediated by increased epinephrine concentrations. Eight healthy volunteers 1) exercised on a bicycle ergometer (60 min, 75% of maximal O2 uptake) and 2) on a later day were given epinephrine as an intravenous infusion to obtain plasma epinephrine concentrations comparable with those seen during exercise. Blood samples were collected in the basal state, during the last minutes of exercise or epinephrine infusion, and 2 h later. The NK cell activity (lysis/fixed number of mononuclear cells) increased during exercise and epinephrine infusion and dropped below basal levels 2 h afterward. The increased NK cell activity during exercise and the epinephrine infusion resulted from an increased concentration of NK (CD16+) cells in the peripheral blood. On the other hand, the decreased NK cell activity demonstrated 2 h after exercise and epinephrine infusion did not simply reflect preferential removal of NK cells from the blood, because the proportion of CD16+ cells was normalized. On the basis of the finding that indomethacin abolished the suppressed NK cell activity in vitro and the demonstration of a twofold increase in the proportion of monocytes (CD14+ cells) 2 h after exercise and epinephrine infusion, we suggest that, after stress, prostaglandins released by monocytes are responsible for downregulation of NK cell function. Our findings support the hypothesis that increased plasma epinephrine during physical stress causes a redistribution of mononuclear subpopulations that results in altered function of NK cells.     

Palatine torus in the Greenlandic Norse.

Physical anthropologists have long been intrigued by the distinctive oral tori expressed by the medieval Norse populations of Iceland and Greenland. To assess the temporal and spatial variation of one form of oral tori, palatine torus, observations were made on all available Greenlandic Norse skeletons, as well as on samples of medieval Icelanders and Norwegians. In terms of temporal variation, 12th to 14th century (medieval) Greenlanders from the Eastern and Western settlements exhibited higher frequencies and more pronounced expressions of palatine torus compared with early 11th century Greenlanders. The early Greenlandic sample closely approximated the medieval Icelandic and Norwegian samples for total torus frequency, although the Norwegians exhibited the trait to a less pronounced degree. As degree of expression is the most distinctive aspect of torus variation among the Norse, some combination of environmental factors, including increased masticatory stress and chronic undernutrition, probably accounts for most of the difference between settlement period and medieval Greenlanders. Although palatine torus may be hereditary in part, environmental factors play a significant role in the expression of this trait.     

Free radical-mediated platelet activation by hemoglobin released from red blood cells.

It is known that the rate of thrombus formation depends on interaction between platelets and erythrocytes, but the mechanism of this process has remained obscure. We here show that nanomolar levels of hemoglobin released from damaged red blood cells can induce platelet aggregation. The molecular mechanism is not receptor-based, but involves oxidation of oxyhemoglobin by platelet-derived hydrogen peroxide, with subsequent generation of a small unknown free radical species, detected by ESR spectroscopy. Methemoglobin and carbon monoxide-treated hemoglobin are unable to cause platelet activation or radical formation. The aggregation of platelets induced by hemoglobin is completely blocked by catalase or radical scavengers. These findings indicate a role for a novel extracellular free radical second messenger in the activation of platelets.     

Two-dimensional NMR, circular dichroism, and fluorescence studies of PP-50, a synthetic ATP-binding peptide from the beta-subunit of mitochondrial ATP synthase.

PP-50, a peptide based on residues 141-190 of the beta-subunit of mitochondrial F1-ATPase, contains the GX4GKT consensus region for nucleoside triphosphate binding and has been shown to bind ATP [Garboczi, D.N., Shenbagamurthi, W.K., Hullihen, J., & Pedersen, P.L. (1988) J. Biol. Chem. 263, 812-816]. At pH 4.0, appropriate for NMR studies, PP-50 retains the ability to bind ATP tightly (KD = 17.5 microM) with a 1:1 stoichiometry as shown by titrations measuring the partial quenching of ATP fluorescence by PP-50. CD spectra of PP-50 at pH 4.0 and at low ionic strength show 5.8% helix, 30.2% beta-structure, and 64% coil. ATP binding increases the structure of PP-50, changing the CD to 7.5% helix, 44.5% beta-structure, and 48% coil. Increasing the ionic strength to 50 mM KCl also increases the structure, changing the CD to 7.4% helix, 64.4% beta-structure, and 28.2% coil. The 600-MHz proton NMR spectrum of PP-50, at pH 4.0 and low ionic strength, has been assigned by 2D methods (TOCSY, DQF-COSY, and NOESY with jump-return water suppression). Based on strong d alpha N NOEs, J alpha N values, and NH chemical shifts differing from random coil values, regions of extended structure are detected from residues 1-7 and 43-48. Based on dNN, dNN(i,i+2), and d alpha N(i,i+2) NOEs and 3J alpha N values, possible type I' and type I turns are found from residues 11-14 and 31-34, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heparin binding to the urokinase kringle domain.

The binding of urokinase to immobilized heparin and dextran sulfate was studied using activity assays of the bound urokinase. The markedly higher binding observed with high M(r) urokinase compared to low M(r) urokinase indicated a role for the amino-terminal fragment (ATF). This was confirmed by the use of inactive truncated urokinase and monoclonal antibodies specific for the ATF in competition assays of urokinase binding. Antibody competition assays suggested a site in the kringle domain, and a synthetic decapeptide Arg-52-Trp-62 from the kringle sequence (kringle numbering convention) was competitive in assays of urokinase binding to dextran sulfate and heparin. Heparin binding to the urokinase kringle was unambiguously demonstrated via 1H NMR spectroscopy at 500 MHz. Effective equilibrium association constants (K(a)*) were determined for the interaction of isolated kringle fragment and low M(r) heparin at pH 7.2. The binding was strong in salt-free 2H2O (K(a)* approximately 57 mM-1) and remained significant in 0.15 M NaCl (K(a)* approximately 12 mM-1), supporting a potential physiological role for the interaction. This is the first demonstration of a function for the kringle domain of urokinase, and it suggests that while the classical kringle structure has specificity for lysine binding, there may also exist a class of kringles with affinity for polyanion binding.     

Simian immunodeficiency virus infection of CD8+ lymphocytes in vivo.

To determine the lymphoid target cells of simian immunodeficiency virus (SIV) in vivo, peripheral blood lymphocytes (PBL) and lymph node lymphocytes (LNL) were positively selected (>97% purity) for surface expression of CD4, CD8, or CD20 and then analyzed for SIV provirus using semiquantitative DNA amplification. We found provirus in CD4+ and CD8+ lymphocytes but none in CD20+ lymphocytes. During acute SIV infection (< or = 214 days postinoculation), the percentage of PBL and LNL CD4+ cells containing proviral DNA ranged from 0.2 to 20% and from 0.2 to 2%, respectively. Proviral burden in the CD8+ population of either PBL or LNL ranged from 0.01 to 0.2%. Virus isolation by cocultivation was positive for both CD4+ and CD8+ purified populations. No difference in proviral burden was observed between PBL and LNL subsets during acute SIV infection. Up to 19.4% of positively selected CD8+ cells also expressed CD4, and thus the provirus may reside within a dual-positive population. This dual-positive population may represent activated lymphocytes that are particularly susceptible to infection and may provide an opportunity for virus entry into the CD8+ CD4- lymphocytes in vivo.     

Use of arbitrarily primed polymerase chain reaction to differentiate Trichophyton dermatophytes

Abstract Dermatophytes such as Trichophyton species are common human pathogens, the infection of which results in dermatophytosis (also known as ringworm). Several laboratory tests are used routinely for the diagnosis of dermatophytosis, but they are either slow or lacking specificity. Through examination of genomic DNA from Trichophyton dermatophytes and other fungi in arbitrarily primed PCR, it was shown that a random primer 5'-ACCCGACCTG-3' produced bands of 4.3 kb, 1.9 kb, 1.7 kb and 0.7 kb in T. rubrum DNA, bands of 2.5 kb, 1.9 kb and 0.8 kb in T. mentagrophytes var. interdigitale and T. mentagrophytes var. mentagrophytes DNA, and bands of 2.5 kb, 1.9 kb, 1.5 kb and 0.9 kb in T. tonsurans DNA. This primer amplified bands of different sizes in other fungal DNA. Therefore, based on the distinct band patterns observed in arbitrarily primed PCR using this primer, T. rubrum , T. mentagrophytes and T. tonsurans dermatophytes could be rapidly differentiated.