Interaction of T-activin with peritoneal macrophages

The action of T-activin on peritoneal macrophages of CBA mice after its introduction into the animals has been studied. In intact mice the phagocytic activity of macrophages and their resistance to the cytopathogenic action of Salmonella typhimurium live cells remains unchanged. The injection of corpuscular pertussis vaccine into mice leads to a decrease in the resistance of macrophages to the action of salmonellae. The simultaneous injection of T-activin into mice in doses of 0.1 and 1.0 microgram per animal abolishes the damaging action of the vaccine. The analysis of the in vitro action of T-activin on macrophages of intact mice revealed that the preliminary incubation of cells with the preparation sharply increases their resistance to the action of salmonellae, while its introduction simultaneously with bacteria or after them rapidly leads to the death of macrophages. The action of T-activin is supposed to be linked with triggering the biosynthetic processes mediating the resistance of macrophages to the cytopathogenic action of salmonellae.     

Effect of T-activin on the production of immune interferon

A study was made of the effect of T-activin on the biosynthesis of immune gamma-interferon. It was shown that in 27% of patients with chronic nonspecific pulmonary diseases, production of gamma-interferon by lymphocytes was substantially reduced during exacerbation of inflammatory process in the lungs. It was discovered that T-activin was not an interferon inductor but enhanced its synthesis in patients with a low capacity of producing immune interferon even at small doses of interferon inductor. The preparation does not produce any effect on this process in normal subjects and in patients showing the normal level of gamma-interferon. Thus T-activin can be used for stimulation of interferonogenesis.     

Stabilization of glucose-6-phosphatase activity by a 21 000-dalton hepatic microsomal protein.

Hepatic microsomal glucose-6-phosphatase activity was rendered extremely unstable by a variety of techniques: (a) incubation at pH 5.0; (b) extraction of the microsomal fraction in the presence of 1% Lubrol; (c) various purification procedures. These techniques all result in the removal of a 21 kDa polypeptide from the fraction containing glucose-6-phosphatase activity. The 21 kDa protein was purified to apparent homogeneity by solubilization in the detergent Lubrol 12A-9 and chromatography on Fractogel TSK DEAE-650(S) and centrifugation at 105 000 g. The 21 kDa protein stabilizes glucose-6-phosphatase activity, whereas other purified hepatic microsomal proteins do not. The 21 kDa protein appears to be a potential regulator of glucose-6-phosphatase activity.     

The importance of membrane integrity in kinetic characterizations of the microsomal glucose-6-phosphatase system

The transport model of glucose-6-phosphatase (EC 3.1.3.9) was recently challenged by a report that detergent treatment had no effect on the presteady state kinetics of glucose-6-P hydrolysis catalyzed at 0 degree C by the enzyme in liver microsomes previously frozen in 0.25 M mannitol (Zakim, D., and Edmondson, D. E. (1982) J. Biol. Chem. 257, 1145-1148). The lack of response to detergent is shown to be the expected consequence of the conditions used in the presteady state measurements. First, when the assay temperature was reduced from 30 to 0 degree C the depression in the glucose-6-P phosphohydrolase activity of intact microsomes (i.e. the system) was much greater than that of fully disrupted microsomes (i.e. enzyme). This indicates that temperature influences transport much more than hydrolysis of glucose-6-P. As a result, the contribution of a small fraction of enzyme associated with disrupted structures is markedly exaggerated, so it becomes the predominant hydrolytic activity before detergent treatment. Second, freezing microsomes in 0.25 M mannitol caused such extensive disruption that all of the activity manifest at 0 degree C could be attributed to enzyme in disrupted structures. The present findings underscore the importance of assessing the state of intactness of "untreated" microsomes and quantifying the contribution of the disrupted component in kinetic analyses of the glucose-6-phosphatase system. The proposition that the detergent-induced changes in the kinetic properties of glucose 6-phosphatase represent removal of constraints imposed on the enzyme by the membrane environment rather than increased access of enzyme to substrate is critically analyzed.     

Comparative glucose and pentose utilization by a thermophilic Lactobacillus

Abstract A thermophilic Lactobacillus , isolate VB183, was tested for comparative glucose and pentose utilization. The possible adverse effect of high concentrations of metabolic end products on cell yield was lessened or eliminated by using low substrate concentrations. Possible growth due to intracellular reserve material, was counteracted by starving the cells for 90 min before being used as inoculant. Isolate VB183 exhibited a higher growth rate on glucose (μ= 1.08 h⁻¹) than on ribose (μ= 0.76 h⁻¹). L. salivarius was included as a pentose non-fermenting control and showed no significant difference between growth on basal medium with and without ribose. VB183 was also found to utilize l (+)-arabinose but not d (−)-arabinose, stressing the importance of the isomer of the sugars tested.     

Potassium-controlled synthesis of heterotopic macrocycles based on isothiosemicarbazide

The macrocyclisation reaction of 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) (1) with S-methylisothiosemicarbazide hydroiodide (H₂NNC(SCH₃)NH₂·HI) in the presence of potassium triflate, followed by addition of M(CH₃COO)₂·nH₂O, where M=Ni, Cu, Zn, afforded [NiLKI₃] (2), [NiLK(CF₃SO₃)] (3), [CuLK(CF₃SO₃)(CH₃OH)] (4) and [(ZnILK)₂CH₃OH] (5), respectively. Compounds 2-5 have been characterised by X-ray crystallography. IR, electronic, mass, ¹H, ¹³C{¹H} and ¹⁹F{¹H} NMR spectra are reported. Magnetic susceptibility measurements and ESR spectra of 4 indicate weak intermolecular spin-spin interactions, which are mostly dipolar in origin.     

Early electrochemical events in lectin-lymphocyte interaction

Concanavalin A, at extremely low concentrations, will produce significant increases in the electrophoretic mobility of murine splenic T lymphocytes. It has been established that the alteration in cellular surface charge is mediated by a factor produced by those lymphocytes that have reacted directly with con A. We originally conjectured that the mobility change might be the consequence of an alteration in the distribution of the charged moieties of membrane glycoproteins. The results of experiments conducted at low temperature raise some questions about this mechanism. Further experiments have been performed to establish the nature of the physicochemical alterations in the peripheral zone of the factor-stimulated lymphocytes that are manifest as changes in cellular surface charge. The results of these studies indicate that, subsequent to the interaction of T lymphocytes with con A, there is a reduction in the number of positively charged amino groups effective at the electrophoretic surface of the cells.     

The glucose-6-phosphatase system in rat hepatic microsomes displays hyperbolic kinetics at physiological glucose 6-phosphate concentrations

The kinetics of rat liver glucose-6-phosphatase (EC 3.1.3.9) were studied in intact and detergent-disrupted microsomes from normal and diabetic rats at pH 7.0 using two buffer systems (50 mM Tris-cacodylate and 50 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) and glucose-6-P varied from 20 microM to 10 mM. Identical data were obtained when the phosphohydrolase activity was quantified by a colorimetric determination of Pi or by measuring 32Pi formed during incubations with [32P]glucose-6-P. In every instance the initial rate data displayed excellent concordance with that expected for a reaction obeying Michaelis-Menten kinetics. The present findings agree with recently reported results of Traxinger and Nordlie (Traxinger, R. R., and Nordlie, R. C. 1987) J. Biol. Chem. 262, 10015-10019) that glucose-6-phosphatase activity in intact microsomes exhibits hyperbolic kinetics at concentrations of glucose-6-P above 133 microM, but fail to confirm their finding of sigmoid kinetics at substrate concentrations below 133 microM. We conclude that glucose-6-P hydrolysis conforms to a hyperbolic function at concentrations of glucose-6-P existing in livers of normal and diabetic rats in vivo.