Effects of N-alkylation and n-acylation on tobramycin activity

The activities of tobramycin derivatives acetylated and ethylated on the 6'-N,2'-N and 3-N positions were examined. The MICs of these derivatives against tobramycin sensitive strains indicated that 2'-N-ethylated and 6'-N-ethylated derivatives have a fairly good activity, and confirmed that the 3-N position is the most important one for antibiotic activity since 3-N derivatives were less active. The MICs of these derivatives against tobramycin resistant strains, and their inactivation by tobramycin modifying enzymes were examined. These results showed that 2'-N or 6'-N ethylation protects the drug against inactivation by AAC(2') or AAC(6'), respectively, and 2'-N-ethyltobramycin and 6'-N-ethyltobramycin were active against strains containing these modifying enzymes. On the other hand, 3-N ethylation protects the drug against inactivation by AAC(3) but 3-N-ethyl tobramycin does not inhibit strains containing this enzyme.

Turnover studies of human beta 2-microglobulin in the rat: evidence for a beta 2-microglobulin-binding plasma protein

1. 125I-labelled beta 2-microglobulin (beta 2m) was injected into rats and protein or non protein-bound radioactivity was determined in plasma urine and several organs. 2. The observed kinetics differed from those expected according to the bicompartmental model for plasma protein turnover. The difference was attributed to the binding of a part of the tracer to a plasma component. Chromatography of plasma taken after injection of beta 2m showed an additional peak of radioactivity at the 55,000-80,000 daltons position. 3. In animals with ligated renal arteries, disappearance of the tracer from the plasma was markedly prolonged, and little non-protein-bound radioactivity was detectable in plasma, indicating that the kidney was the major site of catabolism of beta 2m. 4. Chromatography of plasma from control rats and rats with ligated renal arteries showed that the kidney was the major site of catabolism for free beta 2m only. 5. In normal rats, the urine was found to contain only non-protein-bound radioactivity.

Tentative identification of a second central nervous system myelin membrane autoantigen (M2) by a biochemical comparison with the basic protein (BP)

Two central nervous system myelin autoantigens, M2 and basic protein (BP), were examined, using complement-fixing antibodies against each autoantigen as markers on myelin. M2 activity was very labile and very insoluble, PB activity was very resistant. Trypsin reduced both activities an this reduction was greater after phospholipase treatment. Both activities were slightly solubilized in 8 M urea. It is known that BP is not present on the surface of myelin and is considered a peripheral membrane protein. M2 appears to be a surface and integral membrane protein, and as such resembles Folch Pi proteolipid protein. The relationship between M2 and BP requires further study.

[Presence of glycoproteins binding human beta 2 microglobulin in rat serum]

125I-labeled human beta 2 microglobulin forms complexes with Rat serum glycoproteins. After beta 2m injection in vivo, the serum contains a complex in a 55 K-67 K position. When incubated with Rat serum vitro beta 2m forms additional complexes in greater than or equal to 200 K position. The 55 K complex is partially precipitated by Brown-Norway anti-Lewis alloantiserum.

Elevation of serum beta 2 microglobulin in liver diseases

beta 2 Microglobulin levels were measured by radioimmunoassay in the serum of 160 patients with liver disease and compared to 63 normal controls and 75 asymptomatic HBs-Ag carriers. All the latter subjects had normal values. Elevated serum beta 2 microglobulin levels were found in most of the other categories: acute viral hepatitis (35/45); chronic persistent (8/26) or active (35/41) hepatitis and liver cirrhosis (27/38). beta 2 Microglobulin values were significantly lower in chronic persistent hepatitis than in the three other groups (p less than 0.05). Steroid therapy was followed by reduction of serum beta 2m levels in 11/11 cases of chronic active hepatitis, eight of whom returned to normal value. Although linked to the course of the disease, variations of beta 2 microglobulin were independent of transaminases, bilirubin and gamma globulins. Elevated serum beta 2 microglobulin correlated with demonstration of rheumatoid factor but not with detection of circulating immune complexes, hepatitis B virus markers or autoantibodies. The results suggest that elevation of serum beta w microglobulin is encountered mostly in the active forms of inflammatory liver diseases.

Clq binding circulating immune complexes in multiple sclerosis patients and their first-degree relatives: a distinctive immunological feature between sporadic and familial cases

Circulating Clq binding immune complexes were detected in 43% of sera from sporadic multiple sclerosis patients, in 52% of sera from the patients' first degree relatives and in 12% of normal sera studied, but not in 9 cases of familial multiple sclerosis nor in 24 of their 26 relatives. In sporadic cases, the presence of circulating immune complexes was not associated with any specific clinical form (progressive or remittent) nor with hypocomplementaemia. Circulating immune complexes were found more frequently in female than in males patients, but this sex difference was not found in their healthy relatives. These results indicate that sporadic cases differ from familial multiple sclerosis cases by a frequent occurence of circulating Clq binding immune complexes. Furthermore, the high incidence of immune complexes among relatives of patients with sporadic disease may result either from a genetically controlled immunological disorder or continuing response to an as yet unknow environmental factor.

A sandwich method of enzyme immunoassay. III. Assay for human beta-2 microglobulin compared with radioimmunoassay

A sandwich enzyme immunoassay has been developed to measure human beta-2 microglobulin (beta 2m) in bilogical fluids. beta 2m is first bound by specific antibody covalently coupled to microcrystalline cellulose. The solid phase is washed and reincubated with glucose oxidase-labeled anti-beta 2m antibody. After washing, the enzymic activity of the solid phase is measured by incubation with the appropriate chromogenic substrate. The OD is directly related to the quantity of beta 2m to be measured. A second sandwich assay has also been developed which uses plastic microplates coated with the IgG fraction of rabbit anti-beta 2m serum. Reproducible results are obtained in the range 2-150 and 0.75-48 microgram/l respectively. These tests detect 17 fmoles of beta 2m. Assays of 27 sera showed good agreement between these two enzyme immunoassay methods and two radioimmunoassays.

A two-step synthesis of new water-soluble polymers of NAD+ and ADP. The biological properties of these polymers

Alkylation at the N-1 position of the adenine moiety of NAD+, ADP or ATP with 2,3-epoxypropyl acrylate, followed by polymerization with or without acrylamide at pH 8, gave water-soluble polymers of NAD+ and ADP where the alkyl chain was located at the exocyclic adenine C-6 amino group. Cofactor incorporations were good to high: 145-447 mumol NAD+/g polymer and 667 mumol ADP/g polymer. About 30% of the bound NAD+ could be reduced with rabbit muscle lactae dehydrogenase, yeast alcohol dehydrogenase and Bacillus subtilis alanine dehydrogenase; 84% of the bound ADP was phosphorylated with rabbit muscle creatine kinase. High cofactor activities were obtained with polymerized NAD+ with alcohol dehydrogenase as enzyme: the initial rate of NAD+ polymer reduction was 35-81% that of free NAD+. These values remained substantially high with agarose-immobilized alcohol dehydrogenase (15-36%) and should eventually allow their use in continuous enzymatic reactors. Enzymatic phosphorylation of ADP polymer by creatine kinase gave an ATP polymer with high biological activity: 480 mumol ATP/g polymer were transformed with yeast hexokinase.

Absence of allogeneic restriction in human T-cell-mediated cytotoxicity to Epstein-Barr virus-infected target cells. Demonstration of an HLA-linked control at the effector level

Peripheral T lymphocytes from patients with infectious mononucleosis (IM) are sensitized in vivo against the Epstein-Barr virus (EBV). The expression of HLA-A, B, or C molecules at the target cell surface is necessary for the cytotoxic reaction because (a) EBV-positive Daudi cells lacking HLA-A, B, and C determinants are resistant to anti-EBV T-cell lysis, (b) cytolysis of EBV-positive target cells can be consistently inhibited by anti-HLA-A, B, and C and anti-beta 2 microglobulin antibodies. However, no evidence for allogeneic restriction in this system was apparent as (a) cytotoxic T lymphocytes (CTL) from one given individual could exert a cytotoxicity of a similar magnitude on different EBV-positive target cells, regardless of the number of HLA-A or B specificities shared by the effectors and targets; (b) CTL from IM patients were able to kill target cells without any HLA-A or B antigen in common; and (c) T5-1 variants lacking one or two HLA antigens at the A, B, or D locus are killed to the same extent as the parental cells. 7 of the 9 IM patients with detectable circulating anti-EBV CTL carried the HLA-A1 antigen, whereas none of the 16 IM patients lacking detectable peripheral CTL were HLA-A1 positive (mean specific lysis of T5-1 target cells by T cells from HLA-A1 positive patients: 29.3 vs. 0.6% in HLA-A1-negative patients) (P less than 10(-9)). These data suggest an HLA-A1-linked gene control of the magnitude of the anti-EBV CTL response. Thus, the HLA region appears to act at two different level sin the T-cell-mediated lysis of EBV-infected cells by controlling first, the development of anti-EBV and second, the expression of HLA-A, B, and C molecules involved as recognition structures at the target cell surface.

Elevated serum beta 2-microglobulin levels and C1q-binding immune complexes in sarcoidosis

Serum beta 2 microglobulin levels were found significantly higher (3.05 +/- 0.98 mg/l) in 32 sarcoidosis patients without renal dysfunction than in normal controls (1.54 +/- 0.22 mg/l). Low levels of C1q-binding immune complexes were detected in 70% of patient's sera, despite the absence of extra-thoracic manifestations. C-reactive protein was detected in 55% of sarcoidosis sera. Neither C1q-binding immune complexes nor C-reactive protein were correlated with beta 2 microglobulin levels. Beta 2 microglobulin raised during relapses and fell under efficient corticosteroid treatment. Beta 2 microglobulin would represent a possible biological marker of disease activity.