Mobility and symmetry in the Fc and pFc' fragments as probed by 1H NMR

The 270 MHz ¹H NMR spectra of rabbit Fc and pFc′ fragments appear well resolved when compared to the spectra of other proteins of similar molecular weight. This is interpreted as evidence for substantial segmental flexibility in these fragments. This mobility can be monitored using two special NMR pulse sequences which exploit either the multiplet structure (spin coupling) or the differential linewidths of resonances. Several aromatic residues with mobility independent of the rest of the protein could be detected by these techniques.The titration behaviour of the histidine residues of pFc′ indicates that this fragment possesses a longitudinal C-2 symmetry axis. Of the three pairs of histidines in pFc′, two titrate with pK_a values of 6.8 and 7.3, while the remaining pair remains protonated over the pH range 5.2–8.2 suggesting that these residues are not readily accessible to the solvent. The observation of five pairs of histidine C-2 proton resonances in the Fc indicates that the symmetry axis is retained in this larger fragment.Cleavage of the inter-heavy chain disulphide bond in the Fc fragment has little effect on its NMR spectrum. We find from this that the reduction in complement binding efficiency associated with this cleavage is not a direct consequence of a concomitant large structural change in the Fc fragment.     

Contraction history affects the in vivo quadriceps torque-velocity relationship in humans

We hypothesized that the history of contraction would affect the in vivo quadriceps torque-velocity relationship. We examined the quadriceps torque-velocity relationship of the human knee extensors at the descending and ascending limb of the torque-position relationship by initiating the knee extension at a knee angle position of 1.39 rad (80°) or 0.87 rad (50°) over a 0.52 rad (30°) range of motion under conditions of constant or linearly increasing velocity. Maximal voluntary isometric knee extension torque (M₀) was measured at 1.87 rad, 0.87 rad, and 0.35 rad, and concentric torque was measured. The subjects carried out ten maximal knee extensions at ten distinct velocities, each velocity ranging between 0.52 rad·s^–1 to 5.24 rad·s^–1 in steps of 0.52 rad·s^–1. Peak concentric torque was measured and mean torque calculated from the respective torque-time curves. Peak or mean torque, computed from the individual torque-time curves, and velocity data were fitted to the Hill equation under the four experimental conditions and the curve parameters computed. The M₀ was similar at 0.87 rad and 1.39 rad, but it was significantly lower at 0.35 rad. In the low-velocity domain of the torque-velocity curve where a plateau normally occurs, peak torque was always lower than M₀. Peak and mean torque were significantly greater under linearly increasing velocity conditions and the 1.39 rad starting knee position. Mean torque but not peak torque data could be well fitted to the Hill equation and the two computations resulted in significantly different Hill curve parameters including the concavity ratio, peak power, and maximal angular velocity. We concluded that the history of contraction significantly modifies the in vivo torque-velocity relationship of the human quadriceps muscle. Muscle mechanics and not neural factors may have accounted for the inconsistencies in the human torque-velocity relationships reported previously. Electronic Publication     

Beta-alanine potentiation of [3H]flunitrazepam binding to rat spinal cord homogenates

The effect of beta-alanine, gamma-aminobutyric acid (GABA), and other functionally related amino acids on [3H]flunitrazepam binding to rat spinal cord homogenates was studied. beta-Alanine potentiated [3H]flunitrazepam binding by 40% and GABA by 88%. Taurine increased the binding by 19%. Hypotaurine produced an 11% increase. No significant effect was seen in glycine, alanine, serine, valine or the dipeptide carnosine. The beta-alanine increase in [3H]flunitrazepam binding was completely inhibited by 10 microM strychnine, whereas the GABA increase required 0.1 mM strychnine to be fully suppressed. Results suggest that beta-alanine specifically potentiates binding of [3H]flunitrazepam in rat spinal cord homogenates.     

Lactosamine type asialooligosaccharide recognition in NK cytotoxicity

Inhibition of pig NK cell activity by asialooligosaccharides (aOS) isolated from human serum glycoproteins was investigated. Train-tennary aOS (aOSIII) of ceruloplasmin was found to be the most potent inhibitor up to the concentration 0.1 micrograms/ml, which is in agreement with its highly specific binding to NK-activity-enriched pig lymphocytes (with a morphology similar to human large granular lymphocytes (LGL]. Only lectins with the specificity to Gal(beta 1----4)GlcNAc or Gal(beta 1----3)GalNAc structures exhibited inhibition of NK cytotoxicity. F(ab)2 fragments of rabbit antibodies against pig spleen membrane lectin cross-reacting with the pig liver membrane lectin completely inhibited NK activity when preincubated with the effectors or present in the incubation mixture during the assay. These data suggest that lectin receptors on cells of pig NK-activity-enriched fraction specific for aOSIII and antigenically related to membrane lectins isolated from pig spleen and liver, are involved in the NK recognition of several xenogeneic targets.     

Preparation trauma in stomatology

In this paper authors deal with the causes of preparation trauma in stomatology. They have studied effects of high temperature on human cells cultured in vitro. Based both on literature data and on their own experience they summarize basic principles of preparation which prevent preparation trauma. They summarize how to eliminate as much as possible factors that damage hard dental tissues and pulp.     

Interruption of pregnancy by cervical rivanol predilatation

Experience obtained in 1361 cases of first trimester pregnancy interruption with cervical Rivanol predilatation is reported. Rivanol-induced predilatation of the cervical canal prior to interruption was found to be an efficient procedure. The dilating effect of Rivanol could not be enhanced by i.m. administration of 5 IU oxytocin. After the interruption of more advanced pregnancies a higher degree of dilatation of the cervix was observed. The necessity of further dilatation prior to vacuum aspiration is, in the majority of cases, not higher than 2-2.5 H, which is insignificant on the softened cervix. The immediate complications of medical induction and interruption were infrequent and not severe. Thus, cervical predilatation with Rivanol prior to vacuum aspiration is a recommendable method of pregnancy interruption, worthy of widespread application.     

Antigenic homogeneity among the adenovirus hexon types of subgenus C

Summary Antigenic relationships of hexons of human adenovirus (Ad h) types 1, 2, 5 and 6 of subgenus C were studied with 61 monoclonal antibodies (MAbs) raised against human Ad h1, Ad h35 and bovine adenovirus 2. The reactivity pattern (RP) and the titers of the MAbs were determined in indirect ELISA. In previous experiments with hexons of different subgenera 49 MAbs displayed numerous different intertype specificities besides genus specific and type specific ones. With the four hexon types of subgenus C all MAbs gave identical RPs except the type specific ones. Data reveal the existence of a remarkable homogeneity in the antigenic structure among the hexon types of subgenus C defined by the presence of identical or closely related intertype specific epitopes on the surface of the hexons. The possible significance of the results in the experimental gene therapy is discussed.     

Inhibitory activity of a series of coumarins on leukocyte eicosanoid generation

Sixteen plant-derived or synthetic coumarins with different patterns of substitution were tested for their capacity to modify A23187-induced synthesis of leukotriene B₄ and thromboxane B₂ via the 5-lipoxygenase and cyclooxygenase pathways of arachidonate metabolism in rat peritoneal exudate leukocytes. Five of the 16 coumarins inhibited LTB₄ production: all containortho-dihydroxy substitutions (approximate IC₅₀ values 8–100 M). The mechanism is likely to depend upon a combination of the coumarins' iron-chelating and iron ion-reducing abilities, properties which also confer beneficial activities of these compounds as scavengers of reactive oxygen species (Payá et al., Biochem. Pharmacol.44, 205–214 (1992)). Inhibition of the cyclooxygenase pathway was only demonstrated by one compound, 5,7-dihydroxy-4-methylcoumarin, which did not inhibit 5-lipoxygenase, indicating that the cyclooxygenase inhibitory mechanism is different. Similar effects of the active coumarins were obtained using arachidonic acid as substrate for rat leukocyte eicosanoid generation, confirming that they act at the 5-lipoxygenase/cyclooxygenase level. The same profile of activity was also shown when the coumarins were tested against 5-lipoxygenase in human polymorphonuclear neutrophils. Taken together, these antioxidant and anti-eicosanoid properties of coumarins could be exploited for the design of potentially valuable non-toxic anti-inflammatory agents for treating diseases in which eicosanoid generation and the production of reactive oxygen species are involved.     

Lack of correlation between impaired Interferon production and natural killer activity of lymphocytes in multiple sclerosis

Summary The ability of lymphocytes from patients with multiple sclerosis (MS) to produce Interferon (IFN-) in response to Newcastle Disease Virus (NDV) was studiedin vitro. The correlation between individual IFN- titers and natural killer (NK) cell activity and the presence of HLA system antigens associated with MS (B-7 and DRW-2) was also investigated.Lymphocytes from MS patients showed a significantly impaired capacity to synthesize IFN-in vitro when compared to lymphocytes from healthy donors (mean titers: 85.9 I.U. and 268.2 I.U., respectively). Marked differences in IFN- titers were observed in the group of MS patients.The production of IFN- by the patients' lymphocytes did not correlate with either the activity of NK cells or with their stimulation by exogenous IFN-. There was also no correlation between IFN- production by lymphocytes from MS patients and the presence or absence of B-7 and DRW-2 antigens.With 3 Figures