Excretion of superoxide by phagocytes measured with cytochrome c entrapped in resealed erythrocyte ghosts

Resealed erythrocyte membranes (ghosts) filled with (Fe3+)cytochrome c were used as an assay system to measure the release of superoxide (O-2) from human phagocytes into the incubation medium. Neutrophils, activated by either opsonized zymosan particles or the soluble stimulus phorbol myristate acetate, released O-2, which subsequently entered the ghosts and reduced (Fe3+)cytochrome c. This reaction was dependent on the time of incubation, the concentration of neutrophils, the concentration of stimulus, and the concentration of ghosts. The reaction was completely inhibited by superoxide dismutase and by 4,4'-diisothiocyano-2,2'-disulfonic acid, a specific blocker of anion channels in membranes. The reduction of (Fe3+)cytochrome c free in solution was about four times as fast as the reduction of (Fe3+)cytochrome c in the ghosts. Human eosinophils stimulated by phorbol myristate acetate reacted similarly to human neutrophils; the rate of O-2 production/cell was about twice as high for eosinophils as for neutrophils. In contrast, eosinophils stimulated with opsonized zymosan particles only reduced (Fe3+)cytochrome c free in solution, but not (Fe3+)cytochrome c in ghosts. This lack of reaction was not due to production of an inhibitor or below threshold generation of O-2 for the ghost assay. These results indicate: 1) activated human neutrophils and eosinophils can release O-2 or a similar product into the incubation medium; and 2) reduction of (Fe3+)cytochrome c free in solution is no proof for O-2 excretion by phagocytes.     

No narcosis for bone marrow harvest in autologous bone marrow transplantation

A prospective study with mild general analgesia and sedation together with local anesthesia during bone marrow harvest was performed. Thirty-one patients underwent 33 bone marrow collections. Pretreatment consisted of 100 mg meperidine i.m. and 20 mg diazepam i.m. 1 h before start of procedure. Eight patients got additional meperidine and diazepam during the procedure, all patients got lidocaine 1% locally. A mean volume of 1.321 was obtained with 42.5 punctures. Twenty-two patients had no complications, 4 vomited, 4 had easily correctable hypotension of short duration, one got oxygen for cyanosis of short duration. Acceptance was good in 23 patients, in 6 reasonably well, in two bad. Only one patient experienced pain problems, due to suction. Anxiety was no major problem due to good information before the procedure and mild sedation. This form of anesthesia for bone marrow collection is a safe procedure, it is generally well accepted by the patient and it can be performed on an out-patient basis.     

Reaction of ethyl 2-amino-4,6-O-benzylidene-2-deoxy-d-gluconate with acetylenic esters

Ethyl 2-amino-4,6-O-benzylidene-2-deoxy-d-gluconate adds to acetylenic esters to give sugar enaminones. The following acetylene derivatives have been employed: methyl propiolate, ethyl phenylpropiolate, and dimethyl acetylenedicarboxylate (6). With compound 6, the reaction leads to a mixture of the expected enaminone and the isomeric oxazolidine derivative. The structures and configurations of the new compounds were studied by spectroscopic and chemical methods.     

Lymphokine regulation of human lymphocyte proliferation: Formation of resting G0 cells by removal of interteukin 2 in cultures of proliferating T lymphocytes

The question of whether lymphocytes which have once been activated and have completed one or several cell cycle(s) can return to the G₀ phase and stay ready for a new activation (G₀-G₁ transition), rather than simply die, was investigated. To do so interleukin 2 (IL-2) was removed from cultures of continuously proliferating human T lymphocytes and the formation of resting (G₀) cells was measured. Kinetic analyses in freshly prepared peripheral blood lymphocytes (PBL) revealed that the onset of detectable RNA synthesis and the appearance of structures binding the anti-Tac antibody occurred simultaneously. This allowed the expansion of the definition of G₀ T lymphocytes as cells having a low RNA (and DNA) content, and no Tac antigen. When cultured human T cells proliferating continuously by means of IL-2 were characterized in terms of their distribution in the cell cycle, 7 days after the initial PHA stimulation, it could be demonstrated that very few cells were in the G₀ phase, supporting the concept of direct S/G₂/M-G₁ transition. However, when IL-2 was removed from the cultures, the [³H]thymidine incorporation per 10⁴ cells and correspondingly the number of cells in the S/G₂/M and G₁ phases were reduced drastically and during the following 72-hr period, the number of G₀ cells increased markedly. Restimulation of such in vitro formed G₀ cells, under conditions permitting observation of their shift from the G₀ to G₀ phase, demonstrated that most cells could respond normally. Based on these observations, it was concluded that IL-2 not only ensures T-lymphocyte survival and proliferation, but IL-2 starvation induces many continuously proliferating T lymphocytes to stop cycling and to return to the G₀ phase of the cell cycle where they remain functional.     

Mechanisms of serotonin-induced lymphocyte proliferation inhibition

When human peripheral blood lymphocytes were stimulated with phytohemagglutinin in the presence of serotonin, inhibition of [3H]thymidine incorporation occurred, the most marked inhibition occurring at high (10(-3)M) serotonin concentrations. This effect could not be reversed by the addition of Interleukin 2 (IL-2)-containing supernatants. Cytofluorometric analysis showed that virtually all of the cells remained in the G0 phase (unactivated) at 24 hr while some of the cells entered the G1a and G1b phases of the cell cycle by 42 hr. The cellular production of IL-2 was not affected by serotonin, as supernatants of treated cultures contained essentially the same IL-2 titers as did control cultures. Serotonin seemed to primarily affect cell activation and had little or no effect on proliferating cells. This was further confirmed by the lack of effects of serotonin on a variety of established proliferating lymphocyte, macrophage, and fibroblast cell lines. By contrast, dose-dependent inhibition of IL-2-dependent CTLL cells occurred. Serotonin was not toxic even at 10(-3) M concentrations. A marked decrease in IL-2 receptors and a change in their distribution on responder cells was seen when treated cultures were examined with the anti-Tac monoclonal antibody. At 24 hr this effect was contrastingly not seen for the OKT-8 marker, although a slight decrease in OKT-4-positive cells was seen. Serotonin thus produced an inhibition of lectin-stimulated lymphocyte proliferation via a mechanism independent of IL-2 production, and caused a decrease in the expression and distribution of IL-2 receptors on the surface of responder cells.     

Binding of 5-methoxypsoralen to human serum low density lipoproteins

5-methoxypsoralen (5-MOP) binds to human serum low density lipoproteins (LDL) according to a two-step process. Scatchard analysis of the first step yields K = 1.4 × 10⁵ M^?1 and 4 binding sites. It involves the LDL apoprotein. The second step corresponds to a solubilization, in the lipidic core, of ? 45 molecules of 5MOP per LDL molecule. It is accompanied by a large blue shift of the 5MOP fluorescence. The ability of LDL to bind 5MOP and to carry it into various cells may explain some biological effects sometimes encountered during PUVA therapy.     

Variability and conformation of HLA class I antigens: a predictive approach to the spatial arrangement of polymorphic regions

Comparison of available sequences of HLA-A and HLA-B antigens shows that variable positions are predominantly localized in four segments spanning residues 63-85, 105-116, 138-156, and 177-194. The fourth segment is unique in that it contains no differences between antigens of the same locus. Secondary folding of HLA heavy chain was estimated by three independent predictive methods and areas of defined structure were correlated with the distribution of local hydrophobicity to outline putative internal and external portions. The three analyses each independently predict a high probability for beta structure in the alpha 1, alpha 2, and alpha 3 domains. A single alpha-helix is predicted within residues 146-160, a segment of likely importance in cytotoxic T cell recognition and graft rejection. Substitutions within this segment are spatially related by the helical turn. Variable residues usually lie in areas of high local hydrophilicity, and therefore they are probably on the surface of the molecule. The model predicts that they are frequently located in beta strands, beta-turns, or the above-mentioned alpha-helix, so that most substitutions would be accommodated within rigid frameworks that may impose structural constraints to variability. The secondary structure of alpha 1, alpha 2, and alpha 3 domains presents some analogies that suggest that they might share common features in their tertiary folding. The predicted structure of alpha 3 is strongly reminiscent of that of immunoglobulin constant domains. Possible arrangements of elements of secondary structure are discussed, as an attempt to situating the polymorphic regions of HLA class I antigens in a spatial context.     

Fluorescence method for measuring the kinetics of fusion between biological membranes

An assay is presented that allows continuous and sensitive monitoring of membrane fusion in both artificial and biological membrane systems. The method relies upon the relief of fluorescence self-quenching of octadecyl Rhodamine B chloride. When the probe is incorporated into a lipid bilayer at concentrations up to 9 mol% with respect to total lipid, the efficiency of self-quenching is proportional to its surface density. Upon fusion between membranes labeled with the probe and nonlabeled membranes, the decrease in surface density of the fluorophore results in a concomitant, proportional increase in fluorescence intensity, allowing kinetic and quantitative measurements of the fusion process. The kinetics of fusion between phospholipid vesicles monitored with this assay were found to be the same as those determined with a fusion assay based on resonance energy transfer [Struck, D. K., Hoekstra, D., & Pagano, R. E. (1981) Biochemistry 20, 4093-4099]. Octadecyl Rhodamine B chloride can be readily inserted into native biological membranes by addition of an ethanolic solution of the probe. Evidence is presented showing that the dilution of the fluorophore, occurring when octadecyl Rhodamine containing influenza virus is mixed with phospholipid vesicles at pH 5.0, but not pH 7.4, resulted from virus-vesicle fusion and was not related to processes other than fusion. Furthermore, by use of this method, the kinetics of fusion between Sendai virus and erythrocyte ghosts and virus-induced fusion of ghosts were readily revealed. Dilution of the probe was not observed upon prior treatment of fluorescently labeled Sendai virus with trypsin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Release of dopamine, noradrenaline and dopamine B-hydroxylase from mouse neuroblastoma

The murine C1300 neuroblastoma tumor was found to secrete dopamine, noradrenaline and dopamine B-hydroxylase into the circulation of tumor-bearing A/J mice. The plasma levels of dopamine, noradrenaline and dopamine B-hydroxylase increased with the size of the tumor, and the increase in noradrenaline paralleled the increase in dopamine B-hydroxylase (r = 0.86). The vesicular storage of dopamine and noradrenaline in the tumor was evidenced by a decrease of the tissue content of dopamine and noradrenaline 24 hours after the administration of reserpine (5 micrograms/g) respectively to 17.6% and 7.8% of control values. A similar observation could be made for the levels of dopamine and noradrenaline in the plasma of reserpinized C1300 mice. The total activity of dopamine B-hydroxylase in the tumor and in plasma was unaffected by the reserpine treatment. Chronic administration of 6-hydroxydopamine (100 micrograms/g for 8 days) had no effect on the tissue contents of dopamine, noradrenaline or dopamine B-hydroxylase. The release of catecholamines and dopamine B-hydroxylase from the C1300 neuroblastoma was studied in vitro on superfused tumor slices. Stimulation of these slices with 56 mM KC1 or with 5.10(-5) M tyramine failed to induce the release of endogenous dopamine, noradrenaline or dopamine B-hydroxylase above the basal outflow levels. These results are suggestive for a non-exocytotic release of catecholamines and dopamine B-hydroxylase from the neuroblastoma tumor.     

Repair of UV damage in plasmid DNA by human fibroblasts

Summary Plasmid DNA from Bacillus subtilis was introduced into monolayers of human fibroblasts by means of a modification of the calcium phosphate coprecipitation technique, comprising centrifugation of the coprecipitate onto the cells and treatment with polyethyleneglycol. The amount of DNA resistant to removal from the monolayers ranged from 10% to 15% of the input DNA. By determination of the biological activity of the plasmid DNA, re-extracted after various periods following entry into the fibroblasts and subsequently used as donor for B. subtilis protoplasts, it was shown that the activity of the plasmid DNA was gradually lost. When ultraviolet light-inactivated plasmid DNA was used as donor, reactivation of the plasmid was observed, which was completed within 2 h. The dose-dependent incorporation of [¹⁴C]-thymidine suggests that DNA repair processes were involved in reactivation of the plasmid DNA.