Macrophage-T cell interactions. III. Production from T cells, under the influence of macrophages, of a factor which complexes Ig and antigen.

Soluble complexes of Ig and antigen have been detected in the serum of mice within 6 hr after immunization. Such complexes are taken up by a subpopulation of T cells. We present evidence which suggests that the complexes are formed through the mediation of a factor released from T cells, tentatively called Ig-antigen complexing factor or IACF. IACF is produced as a result of a macrophage/T-cell interaction, when macrophages are present in an optimal proportion in relation to T cells (4%). Particulate or aggregated substances stimulate macrophages to release a mediator which subsequently acts on Fc receptor-negative T cells to produce IACF. Free-SH groups are important for the activity of the macrophage mediator. Mercaptoethanol and l-cysteine can also release IACF from T cells in the absence of macrophages. Protein synthesis is necessary for the production of this factor, the activity of which is abolished by trypsin digestion. It is postulated that the complexes of Ig and antigen formed under the influence of IACF represent a mechanism of presentation of antigen to T cells.     

Influence of the lactose plasmid on the metabolism of galactose by Streptococcus lactis.

Streptococcus lactis strain DR1251 was capable of growth on lactose and galactose with generation times, at 30 degrees C, of 42 and 52 min, respectively. Phosphoenolpyruvate-dependent phosphotransferase activity for lactose and galactose was induced during growth on either substrate. This activity had an apparent K(m) of 5 x 10(-5) M for lactose and 2 x 10(-2) M for galactose. beta-d-Phosphogalactoside galactohydrolase activity was synthesized constitutively by these cells. Strain DR1251 lost the ability to grow on lactose at a high frequency when incubated at 37 degrees C with glucose as the growth substrate. Loss of ability to metabolize lactose was accompanied by the loss of a 32-megadalton plasmid, pDR(1), and Lac(-) isolates did not revert to a Lac(+) phenotype. Lac(-) strains were able to grow on galactose but with a longer generation time. Galactose-grown Lac(-) strains were deficient in beta-d-phosphogalactoside galactohydrolase activity and phosphoenolpyruvate phosphotransferase activity for both lactose and galactose. There was also a shift from a predominantly homolactic to a heterolactic fermentation and a fivefold increase in galactokinase activity, relative to the Lac(+) parent strain grown on galactose. These results suggest that S. lactis strain DR1251 metabolizes galactose primarily via the tagatose-6-phosphate pathway, using a lactose phosphoenolpyruvate phosphotransferase activity to transport this substrate into the cell. Lac(-) derivatives of strain DR1251, deficient in the lactose phosphoenolpyruvate phosphotransferase activity, appeared to utilize galactose via the Leloir pathway.     

INTRACELLULAR PHYTOCHROME DISTRIBUTION AS A FUNCTION OF ITS MOLECULAR FORM AND OF ITS DESTRUCTION

The immunocytochemically observed intracellular redistribution of phytochrome as a function of its molecular form is described by utilizing color photomicrography. The reversible change from a diffuse to a discretely localized distribution following photoconversion of the red-absorbing Pr form to the far-red-absorbing Pfr form observed with etiolated oat (Avena sativa L., cv. Garry) coleoptile parenchyma cells is not seen with etiolated wheat (Triticum sativum L., cv. unknown), barley (Hordeum vulgare L., cv. Harrison), or rye (Secale cereale L., cv. Balbo). Whether redistribution in these latter cases does not occur or is below the limit of detection is not known. Upon continuous actinic irradiation, phytochrome, which is discretely localized as Pfr, rapidly disappears by both immunocytochemical and spectral assay. However, after about 90 min irradiation, a new association of phytochrome with nuclei is evident which is more pronounced after 4 or 8 h of irradiation. With longer irradiation times there is a total loss of antigenically detectable phytochrome at the resolution employed in these experiments.     

Large-scale isolation and partial purification of type C RNA viruses on hydroxyapatite. 1. Biochemical characterization.

A chromatographic procedure utilizing common laboratory equipment and based on the batchwise adsorption of type C RNA virus onto hydroxyapatite for the concentration and partial purification of viruses from large volumes of tissue culture fluid has been developed. This procedure provides an alternative to the use of elaborate and expensive high-speed zonal ultracentrifuge equipment. The viruses obtained by this procedure have a buoyant density of 1.16 g/cm³, contain 70 S RNA, an RNA-directed DNA polymerase (reverse transeriptase), surface glycoproteins ($\text{GP}\text{69}\text{71}$), and the internal viral specific polypeptides p10 to 15 and p27 or p30.     

Contributions of aerobic and anaerobic energy production during swimming in the bivalve molluscLimaria fragilis (family limidae)

Summary Oxygen consumption rates ( ) and a number of possible anaerobic end products were determined forLimaria fragilis at rest, and following active swimming. increased up to 8-fold (=4) during swimming. Swimming did not change the concentrations ofl-lactate, alanine or arginine phosphate in the single striated fast adductor muscle. Octopine, succinate andd-lactate were not detected in the adductor muscles of resting or active animals (<0.2 moles/g wet weight).It is concluded that the slow sustained swimming displayed byLimaria utilises predominantly aerobic mechanisms of ATP production.     

An improved method of light-induced pigmentation.

An improved procedure was developed whereby a primary light signal can be intensified and made visible by activation of a pre-tyrosinase (pre-phenoloxidase) enzyme [isolated from silkworm (Bombyx mori)] by alpha-chymotrypsin; this activation results from the light-activated conversion of the inactive cis-cinnamoyl-alpha-chymotrypsin.     

Influence of trace elements and nitrogen sources on versicolorin production by a mutant strain of Aspergillus parasiticus

A mutant strain of Aspergillus parasiticus blocked in aflatoxin biosynthesis accumulates versicolorin A and versicolorin C. The effect of trace elements on the growth and versicolorin production by this strain was studied in a defined medium. The omission of manganese was slightly stimulatory to versicolorin production; when zinc was omitted from the medium, no detectable versicolorins were produced. Experiments on nitrogen sources in a highsucrose medium indicated that fourfold to fivefold increases in versicolorin yields could be obtained by substituting 3 ml/l corn steep liquor or 0.1 M NH₄NO₃ for the 0.023 M (NH₄)₂SO₃ used previously as the nitrogen source in studies on versicolorin production by this strain. These improved yields will facilitate attempts to accumulate enough versicolorin A and versicolorin C for toxicity and carcinogenicity testing. Chromatographic profiles of mycelial extracts of cultures grown in a defined medium with 0.1 M NH₄NO₃ as the nitrogen source revealed 2 previously unrecognized compounds. The accumulation of these new metabolites in a mutant blocked in aflatoxin production may indicate that they are biosynthetically related to aflatoxin.