Functional analysis of human T cell subsets defined by monoclonal antibodies. V. Suppressor cells within the activated OKT4+ population belong to a distinct subset

In the present report, we characterize a monoclonal antibody directed at a surface differentiation antigen on human T cells. The monoclonal antibody, OKT17, recognizes a cell surface antigen present on the majority of resting normal peripheral T cells. In contrast, OKT17 is unreactive with normal B cells, B cell lines, T cell lines, or SIg+ CLL. Interestingly, after activation, the antigen recognized by OKT17 is lost from a subset of OKT4+ cells. We took advantage of this finding to explore further the functional heterogeneity within activated OKT4+ cells. Evidence was obtained that the PWM-activated OKT4+ subset remaining after depletion of OKT17-reactive T cells (OKT4+ 17-) contains radiosensitive helperr cells but is devoid of suppressor cells. In contrast, the activated OKT4+ 17+ population contains potent radiosensitive suppressor cells as well as radioresistant helpe cells. Taken together, these studies suggest that the OKT17 monoclonal antibody can differentiate two functionally mature, activated OKT4+ human T cells: OKT4+ OKT17+ radiosensitive suppressor cells and OKT4+ 17- radiosensitive helper cells.     

Effect of monensin on osmotic water flow across the toad bladder and its stimulation by vasopressin and cyclic AMP

Summary The effects of the sodium ionophore monensin on osmotic water flow across the urinary bladder of the toadBufo marinus were studied. Monensin alone did not alter osmotic water flow; however, the ionophore inhibited the hydrosmotic response to vasopressin and cyclic AMP in a dose-dependent manner. The inhibitory effects of monensin were apparent when the ionophore was added to the serosal bathing solution but not when it was added to the mucosal bathing solution. The inhibitory effect of serosal monensin required the presence of sodium in the serosal bathing solution but not the presence of calcium in the bathing solutions. Thus, it appears that intracellular sodium concentration is a regulator of the magnitude of the hydrosmotic response to vasopressin and cyclic AMP.     

Hormone-dependent terminal differentiation in vitro of chicken erythroleukemia cells transformed by ts mutants of avian erythroblastosis virus

Chicken erythroblast cell strains and a cell line transformed by ts mutants of avian erythroblastosis virus (AEV) terminally differentiate when shifted to the nonpermissive temperature (42°C). The differentiated cells resemble mature erythrocytes with respect to morphology and ultrastructure, expression of differentiation-specific cell-surface antigens, pattern of protein synthesis and hemoglobin content. Terminal differentiation is dependent on conditions favoring the differentiation of normal erythroid progenitor cells, including an erythropoietin-like factor. Colonies of ts AEV cells grown at 42°C in semisolid medium resemble erythrocyte colonies derived from normal erythroid progenitor cells. The colonies obtained were comparable in size or slightly larger than the late erythroid precursor (CFU-E) colonies. These results suggest that AEV-transformed cells are blocked at a stage of differentiation that is more advanced than that of the uninfected target cells. ts AEV cells are irreversibly committed to terminal differentiation within 20 to 30 hr after shift to 42°C.     

The pollination biology of Calypso bulbosa var. Americana (Orchidaceae): Initial deception of bumblebee visitors

Summary The orchid Calypso bulbosa var. americana has deceptive flowers that provide no rewards for visitors. Near Banff, Alberta, the flowering period of this species is synchronized with the emergence of its pollinators, large bumblebee queens, in late spring. Calypso flowers appear to rely on the initial attraction and deception of newly-emerged naive bumblebees for pollination. Indirect evidence suggests that individual bees subsequently learn to avoid these flowers and that avoidance is learned quite rapidly. Avoidance behavior by pollinators is obviously detrimental to sexual reproduction in Calypso. This negative effect appears to be offset by the large number of seeds produced in plants which are effectively pollinated. A test of the hypothesis that Calypso flowers mimic flowers of the shooting star, Dodecatheon radicatum (Primulaceae) failed to provide evidence for mimicry.     

Phytochrome Regulation of Flowering in the Long-Day Plant, Hyoscyamus niger

A daylength extension with incandescent light is more effective in promoting flowering of long-day plants like Hyoscyamus niger than fluorescent light. A low phytochrome photoequilibrium (Pfr/P_tot), attained by a far-red irradiation at the close of long days under fluorescent light, also promotes flowering. Moreover, if flower initiation processes are initiated by several long days, a low phytochrome photoequilibrium at the end of short, postinduction photoperiods also enhances flowering. The initiation phase of flowering requires Pfr to be present whereas the development phase proceeds more rapidly in the absence of Pfr. Spectral dependence studies, therefore, could be misinterpreted if the initiation and development stages are combined into a single audit of flowering.     

The effect of plant-hormone pretreatments on ethylene production and synthesis of 1-aminocyclopropane-1-carboxylic acid in water-stressed wheat leaves

Excised wheat (Triticum aestivum L.) leaves, when subjected to drought stress, increased ethylene production as a result of an increased synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC) and an increased activity of the ethyleneforming enzyme (EFE), which catalyzes the conversion of ACC to ethylene. The rise in EFE activity was maximal within 2 h after the stress period, while rehydration to relieve water stress reduced EFE activity within 3 h to levels similar to those in nonstressed tissue. Pretreatment of the leaves with benzyladenine or indole-3-acetic acid prior to water stress caused further increase in ethylene production and in endogenous ACC level. Conversely, pretreatment of wheat leaves with abscisic acid reduced ethylene production to levels produced by nonstressed leaves; this reduction in ethylene production was accompanied by a decrease in ACC content. However, none of these hormone pretreatments significantly affected the EFE level in stressed or nonstressed leaves. These data indicate that the plant hormones participate in regulation of water-stress ethylene production primarily by modulating the level of ACC.Abbreviations ABA abscisic acid - ACC 1-aminocyclopropane-1-carboxylic acid - BA N⁶-benzyladenine - EFE ethylene-forming enzyme - IAA indole-3-acetic acid     

The endogenous gibberellins of vegetative and reproductive tissue of G2 peas

The gibberellins (GAs) of both vegetative (leaves and stems) and reproductive (pods and seeds) tissue of the G2 strain of peas Pisum sativum L. were characterized in purified extracts by a combination of sequential silicic-acid partition column chromatography, and gas chromatography-mass spectrometry. Gibberellins A₁₉, A₂₀, A₂₉ and an A₂₉ catabolite were identified in both types of tissue. Gibberellins A₉, A₁₇ and A₄₄ were also found in pods and seeds.Abbreviations FID Ilame ionization detector - GA(s) gibberellin(s) - GC gas chromatograph(y) - HPLC high performance liquid chromatograph(y) - LD long day - MS mass spectrum(a) or mass spectrometer(ry) - SD short day     

Spoilage association of chicken skin.

The bacterial succession on the skin of broiler chicken carcasses stored at 2 degrees C was traced, and the ability of representative isolates to produce off-odors was determined by using sterile leg and breast muscle sections. Off-odors were identified by olfactory and chemical means. The inability of peptone-iron agar to detect sulfide-producing strains was noted.     

Steroidal control of rat uterine 17β-hydroxysteroid dehydrogenase activity

The interconversion of estradiol-17β and estrone in the rat uterus is due to the action of 17β-hydroxysteroid dehydrogenase. Whole uteri or 800 × g supernatant fractions of the uteri were incubated in the presence of [³H] estradiol-17β and NAD at 37°C for 3 h or 1 h, respectively. In the mature rat uterus the oxidation of estradiol-17β and estrone was dependent on the stage of the estrous cycle, suggesting hormonal control. The 17β-hydroxysteroid dehydrogenase activity was highest at estrus (200 fmol estrone) and lowest at diestrus (80 fmol estrone). An enhancement of activity occurred when adult rats at each stage of the estrous cycle were administered estradiol-17β, while progesterone administration at each stage resulted in decreased enzyme activity. The uterine 17β-hydroxysteroid dehydrogenase activity of estradiol-17β treated ovariectomized rats was time and dose dependent but decreased when progesterone was administered with or without estradiol-17β administration. These results suggest that estradiol-17β caused an increase in enzyme activity that was inhibitable by progesterone in the rat uterus. The increased 17β -hydroxysteroid dehydrogenase activity may reflect a specific response of the rat uterus to estradiol-17β.