Modulation of natural killer activity by thymosin alpha 1 and interferon

Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin ₁ cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin ₁ (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin ₁ was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin ₁ and -IFN could be the result of effects on differentiation of the NK lineage at different levels.     

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.     

Global stability in time-delayed single-species dynamics

Criteria are established for three classes of models of single-species dynamics with a single discrete delay to have a globally asymptotically stable positive equilibrium independent of the length of delay. Research partially supported by the NSERC of Canada, grant No. A4823. Research was carried out while the author was a distinguished visitor at the University of Alberta.     

Outdoor mass culture of Spirulina maxima in sea-water

Summary The results of a whole year experiment on the outdoor mass culture of Spirulina maxima strain 4Mx on fertilized sea-water are reported. Carbonate and phosphate precipitation in the sea-water media was prevented by maintaining a low concentration of phosphate and by controlling the pH in the range of 8.0–8.3. The mean annual yield of biomass on sea-water plus urea as nitrogen source was 7.35 g (dry weight) m^-2· day^-1, a value slightly lower than that obtained on the standard bicarbonate medium (8.14 g · m^-2 · day^-1). On sea-water plus nitrate the yield was only 5.2 g·m^-2·day^-1. The nitrogen content of the biomass was higher in summer and lower in winter. The seasonal effect was more evident when nitrate was the nitrogen source.     

Calmodulin-stimulated protein kinase activity from rat pancreas

Previous work from our laboratory has demonstrated that neurohumoral stimulation of the exocrine pancreas is associated with the phosphorylation of the Mr 29,000 ribosomal protein S6. In a cell-free system using pancreatic postmicrosomal supernatant as the kinase donor, we found that the following co-factors stimulate the phosphorylation of the Mr 29,000 ribosomal protein: calcium with calmodulin, calcium with phosphatidyl serine, and cAMP. These findings suggest that the pancreas contains a calcium-calmodulin-dependent protein kinase (CaM-PK) that can phosphorylate the Mr 29,000 ribosomal protein. A CaM-PK activity was partially purified sequentially by ion exchange, gel filtration, and calmodulin-affinity chromatography. Phosphorylation of the Mr 29,000 ribosomal protein by the partially purified CaM-PK was dependent on the presence of both calcium and calmodulin and not on the other co- factors. The CaM-PK fraction contained a phosphoprotein of Mr 51,000 whose phosphorylation was also dependent on calcium and calmodulin. When 125I-calmodulin-binding proteins from the CaM-PK fraction were identified using electrophoretic transfers of SDS-polyacrylamide gels, a single Mr 51,000 protein was labeled. The preparation enriched in CaM- PK activity contained an Mr 51,000 protein that underwent phosphorylation in a calcium-calmodulin-dependent manner and an Mr 51,000 calmodulin-binding protein. It is therefore possible that the CaM-PK may comprise a calmodulin-binding phosphoprotein component of Mr 51,000.     

Membrane potentials associated with Ca-induced K conductance in human red blood cells: Studies with a fluorescent oxonol dye,WW 781

Summary A divalent anionic dye, bis-[3-methyl-1-p-sulfophenyl-5-pyrazolone-(4)]-pentamethine oxonol (WW 781) is a rapidly responding fluorescent indicator of KCl diffusion potentials induced in human red blood cells with valinomycin, gramicidin, and with the Ca ionophore A 23187 in the presence of external Ca. WW 781 has a sensitivity of 0.13% F/mV, a detection limit of 10 mV, a response time of less than 1 sec, and exhibits a decrease in fluorescence intensity upon hyperpolarization without detectable shifts in absorption or emission peaks. This dye does not perturb the normal resting potential, and unlike the slow permeant cyanine dyes, does not inhibit Ca-induced K conductance in human red blood cells. However, WW 781 does stimulate Ca-induced unidirectional Rb efflux. With Ca plus A 23187, the initial rapid change in dye fluorescence is sensitive to [Ca] _o and to [A 23187], is reversible with excess EGTA, and is inhibited by quinine, oligomycin, and by trifluoperazine. A biphasic dependence of hyperpolarization on K _o is evident at pH 6, where the ionic selectivity of activation is K, Rb>Cs>Na and that of conductance is K, Rb>Cs. Conditions were defined which permitted continuous monitoring ofE _m for at least 10 min, and the time dependence of the Ca-induced potentials was characterized. Since the properties of the Ca-induced changes in dye fluorescence correlate well with the known characteristics of Ca-induced K permeability, we conclude that WW 781 is a useful indicator of changes inE _m, provided that sufficient controls are employed to separate direct effects of Ca on dye fluorescence from the effects ofE _m on fluorescence.     

Protein kinase activity of purified components of the chicken oviduct progesterone receptor

Preparations of the 90K and 110K components of the chick oviduct progesterone receptor (PR) purified to near homogeneity were tested for protein kinase activity. The 90K component was shown to incorporate radioactive phosphate from [γ-³²P]-ATP in the presence of Ca²⁺ but not of Mg²⁺ ions, while the 110K component was phosphorylated in the presence of Mg²⁺, but not of Ca²⁺. The enzymatic activity of the 90K polypeptide appeared selective, since added proteins (histones) did not become phosphorylated. However, all proteins present in the 110K preparations were phosphorylated in the presence of Mg²⁺. These data suggest that components of the chick oviduct PR display protein kinase activity.     

Modulation of endogenous prostaglandins by thymosin-α1 in lymphocytes

The effects of thymosin-α₁ on the stimulation of specific release of prostaglandin E₂ (PGE₂) from splenic lymphocytes and thymocytes were studied. Experiments were also performed to study in parallel the absolute levels of thymosin-α₁ in the blood and the induction of serum FTS activity and of azathioprine sensitivity of spleen cells from adult thymectomized (ATx) mice. A significant difference in the release of PGE₂ between normal splenocytes and splenocytes from ATx mice was observed. Thymosin-α₁ at certain concentrations was able to stimulate PGE₂ release from lymphocytes of ATx mice while inhibiting release in lymphocytes of normal mice. Also, thymocytes were stimulated to release PGE₂ after incubation with α₁ in a manner similar to that seen in spleen cells of ATx mice. Approximately the same concentration of α₁ was found to also correct the low azathioprine sensitivity of splenocytes from ATx mice. Determinations of FTS-like activity in the blood and the pharmacokinetics of α₁ after administration of this synthetic molecule show a clear dissociation. A maximum peak of α₁ activity was obtained after 1 hr, while maximal FTS-like activity was observed after 24 hr. The inhibition of the induction by α₁ of FTS-like activity and of Thy 1.2 antigen by indomethacin suggests that the action of α₁ requires prostaglandin biosynthesis.     

Potassium Uptake in Synchronous and Synchronized Cultures of Escherichia coli

Criteria are presented for distinguishing between synchronous and synchronized cultures (natural vs. forced synchrony) on the basis of characteristics of growth and division during a single generation. These criteria were applied in an examination of the uptake of potassium during the cell growth and division cycle in synchronous cultures and in a synchronized culture of Escherichia coli. In the synchronous cultures the uptake of ⁴²K doubled synchronously with cell number, corresponding to a constant rate of uptake per cell throughout the cell cycle. In the synchronized culture, uptake rates also remained constant during most of the cycle, but rates doubled abruptly well within the cycle. This constancy of ⁴²K uptake per cell supports an earlier interpretation for steady-state cultures that uptake is limited in each cell by a constant number of functional sites for binding, transport, or accumulation of compounds from the growth medium, and that the average number of such sites doubles late in each cell cycle. The abrupt doubling of the rate of uptake of potassium per cell in the synchronized culture appears because of partial uncoupling of cell division from activation or synthesis of these uptake sites.