Metabolic inhibition of size-fractionated marine plankton radiolabeled with amino acids,glucose, bicarbonate,and phosphate in the light and dark

The effects of various metabolic inhibitors (dichlorophenyl dimethylurea, chloramphenicol, cycloheximide, carbonyl cyanide m-chlorophenyl hydrazone) on the accumulation of radiolabeled substrates (amino acids, glucose, bicarbonate, phosphate) by size-fractionated marine microbial plankton from the Sargasso Sea and the eastern Canadian arctic were studied in time-course fashion during experimental incubations either exposed to or shielded from ambient solar radiation. Picoplankton accounted for 65% of the organic substrates and phosphate accumulated by the assemblages. The rate of organic substrate accumulation was stimulated by solar radiation in some cases but inhibited in other cases. Presumably, stimulation and inhibition co-occur and the measured response is the net result arising from these counteracting tendencies. Approximately 40% of H¹⁴ CO₃ ^– accumulation in the Sargasso Sea was associated with the picoplankton. The insensitivity of picoplankton¹⁴C-labeling to cycloheximide suggested active prokaryotic photosynthesis rather than heterotrophic assimilation of¹⁴C-labeled algal photosynthates as the route of labeling. The usefulness of some inhibitors was restricted in this study because of inconsistent correlations between the intended primary metabolic effect and the measured ecological response within the duration of the experiment.     

T and B cells induce macrophages which suppress proliferation but not lymphokine secretion

In vitro culture of mouse spleen cells for 2 days or more leads to the production of adherent, phagocytic, Thy-1-, Ia+, Lyt-2- cells ("suppressor macrophages") which strongly inhibit the proliferative response of T and B lymphocytes to a variety of stimuli: mitogens, specific antigens, and antigen-nonspecific growth factors. Suppressive activity fails to develop, however, in cultured spleen cells from which nonadherent cells have been removed before the initial 48-hr incubation, and only partial suppression is obtained from cell suspensions from which T cells have been depleted before culture. We find that the requirement for nonadherent cells can be replaced by graded doses of lymphocytes. Lyt-2- and Lyt-2+ T cells are about equally potent in inducing suppressive activity in nonadherent cells. Surprisingly, B cells (containing fewer than 0.1% contaminating T cells) are also able to induce suppression in this system. The suppression induced includes both indomethacin-sensitive and indomethacin-resistant components. Interestingly, not all stages of mitogen-induced T-cell activation are blocked by these adherent cells: proliferation is inhibited, but production of interleukin 2 (IL-2) and interleukin 3 (IL-3) is unaffected.     

Effect of physico-chemical factors on anion-sensitive ATPase activity

Effects of temperature, pH and anions on the ATPase activity of submitochondrial particles of rat liver, rat heart, mouse liver, of red blood cell membranes, and of soluble enzyme of rat liver, mouse liver mitochondria were studied. The temperature relationships of membrane-bound and soluble ATPases have the breaks at 18-21 degrees C and 30-32 degrees C. These breaks were not shifted by sulfite, thiocyanate, methanol, glycerol and GTP. The pH changes from 6.0 to 8.5 produced no effect on the temperature relationships of ATPase activities but, strongly influenced the rate of ATPase reaction. The conformity between the obtained data and earlier proposed mechanism of anion control over anion-sensitive ATPase activity was discussed.     

Modulation induction of the T3 antigen by OKT3 antibody is monocyte dependent

We investigated the influence of monocytes on the susceptibility of the T3 antigen on human T cells to modulation induction by OKT3 antibody. In the absence of monocytes, the T3 antigen was only minimally susceptible to modulation. After the addition of 20% monocytes to the culture, however, complete modulation was readily observed. Furthermore, we found that even in the absence of OKT3 antibody, monocytes were able to down-regulate the expression of the T3 antigen, although to a lesser extent. The ability of monocytes to enhance antigenic modulation proved to be a more general phenomenon. Each individual T cell antigen, however, differed in its susceptibility to modulation by antibody, monocytes, or both, thereby establishing its own characteristic pattern. In addition, after complete modulation of the T3 antigen, the addition of monocytes to the culture thereafter had a distinct inhibitory effect on the reexpression of the T3 antigen. Monocyte enhancement of T3 modulation is significantly reduced when using the OKT3 F(ab')2 fragment, as is OKT3 mitogenesis. After pulsing the monocytes with OKT3 antibody before adding them to the culture, T3 modulation became nearly complete even in the absence of added OKT3 antibody. Monocyte-induced modulation proved not to be MHC restricted, thus allowing for comparative analysis of this effect between monocytes and other cell types. A moderate, however, incomplete modulation enhancement was observed with the human monocyte cell line U937 and with Daudi cells. This finding proved to coincide with the distinct ability of these cell lines to bind OKT3 antibody by their Fc receptors, as was the case with monocytes. In contrast, neither Fc receptor binding nor T3 modulation enhancement was observed with the cell lines Cess and G7. In addition, no effective T3 modulation was observed with glutaraldehyde-fixed monocytes. The overall results seem to indicate that effective modulation of the T3 antigen by OKT3 antibody requires the active participation of Fc receptors on monocytes.     

Application of macroscopic balances to the identification of gross measurement errors

A systematic method is presented which is capable of both detecting the presence of grossly biased measurement errors and locating the source of these errors in a bioreactor through statistical hypothesis testing. Equality constraints derived from material and energy balances are employed for the detection of data inconsistencies and for the subsequent identification of the suspect measurements by a process of data analysis and rectification. Maximum likelihood techniques are applied to the estimation of the states and parameters of the bioreactor after the suspect measurements have been eliminated. The level of significance is specified by the experimenter while the measurments are assumed to be randomly, normally distributed with zero mean and known variances. Two different approaches of data analysis, batchwise and sequential, that lead to a consistent set of adjustments on the experimental values, are discussed. Several examples based on the fermentation data taken from literature sources are presented to demonstrate the utility of the proposed method, and one set of data is solved numerically to illustrate the computational aspect of the algorithm.     

A modified method of UDS detection in vitro suitable for screening the DNA-damaging effects of chemicals

The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test.     

Synthesis of a peptide with full somatostatin activity

A peptide has been synthesized according to the structure proposed for somatostatin by the solid phase method. The synthetic product was assayed and found to possess full somatostatin activity as compared with the natural material.