Influence of Organic-Phosphates on 3-Phosphoglycerate Dependent O2 Evolution in C3 and C4 Mesophyll Chloroplasts

In C₄ plants phosphoenolpyruvate (PEP) of the C₄ cycle may betransported on a chloroplast transporter which also transports3-phosphoglycerate (3-PGA) and triosephosphates. In C₃ plantsPEP is not considered to be effectively transported on the chloroplastphosphate translocator. The influences of certain organic phosphates,having a similar structure to either PEP or triose-phosphates,on 3-PGA dependent O₂ evolution by C₄ (Digitaria sanquinalisL. Scop.) and C₃ (Hordeum vulgare L.) mesophyll chloroplastswere investigated. In the C₄ mesophyll chloroplasts phosphoglycolatewas a competitive inhibitor (K_i = 2.1 mM) of 3-PGA dependentO₂ evolution, and was as effective as previously reported forPEP. 2-Phosphoglycerate was also a competitive inhibitor (K_t= 8.6 mM) of O₂ evolution in the C₄ mesophyll chloroplasts with3-PGA as substrate, while phospholactate was a weak inhibitorand glyphosate had no effect. Neither PEP, phosphoglycolatenor 2-phosphoglycerate were effective inhibitors of 3- PGA dependentO₂ evolution in the C₃ chloroplasts. Phosphohydroxypyruvatewas a competitive inhibitor of 3-PGA dependent O₂2 evolutionin both chloroplast types. The selectivity in inhibition ofO₂ evolution with 3-PGA as substrate suggests that the C₄ mesophyllchloroplasts can recognize certain organic phosphates with thephosphate in the C-2 or C-3 position but that the C₄ mesophyllchloroplasts can only effectively recognize certain organicphosphates with the phosphate in the C-3 position. The resultsalso support the view that 3-PGA and PEP are transported onthe same phosphate translocator in C₄ mesophyll chloroplasts. ¹ Current address: Department of Horticulture, 2001 Fyffe Court,The Ohio State University, Columbus, Ohio 43210-1096. (Received March 24, 1987; Accepted April 16, 1987)     

Study on the enzymatic 5′-deiodination of 3′,5′-diiodothyronine using a radioimmunoassay for 3′-iodothyronine

A radioimmunoassay for 3′-iodothyronine has been developed. All iodothyronine analogues (except 3,3′-diiodothyronine) showed very little (0.02% at most) cross-reactivity, and the assay was sensitive to 1 pg 3′-iodothyronine/ tube. We have studied the 5′-deiodination of 3′,5′-diiodothyronine by rat liver microsomal fraction in the presence of dithiothreitol. Production of 3′-iodothyronine at 37°C was found to be linear with time of incubation up to 30 min and with concentration of microsomal protein up to 100 μg/ml. The reaction rate reached a limit on increasing 3′,5′-diiodothyronine concentration to 10 μM. The effect of pH on 3′-iodothyronine production was found to depend on 3′,5′-diiodothyronine concentration. Increasing 3′,5′-diiodothyronine concentration from 0.1 to 10 μM resulted in a shift of the pH optimum from 6–6.5 to 7.5. Similar effects on the 5′-deiodination of 3,3′,5′-triiodothyronine were observed, supporting the hypothesis that these reactions are catalysed by a single enzyme (iodothyronine 5′-deiodinase).     

Moral medicine: Symbolic content in 19th century Shaker therapeutics

This paper presents an analysis of the symbolic meanings implicit in an ostensibly empirical therapeutic system. The Shakers, a celibate communal religious order founded in New York State in the mid 1770s, were practitioners of botanic medicine, as were many other Americans in the nineteenth century. This study analyzes the therapeutic properties of the herbs they produced (such as diuretic, stimulant, narcotic, emetic, astringent), using a classification scheme based on the location of the botanical substance's effect vis-à-vis body boundaries and surfaces. The Shakers' beliefs about the therapeutic properties of their herbs are compared with similar analyses of the properties given by two contemporary nineteenth century New England proponents of herbal medicine, botanist Constantine Rafinesque and sectarian practitioner Samuel Thomson. The comparison shows systematic variation in emphasis given to herbs which regulate internal body processes, or act through the openings of the body or on its surface. In this context Shaker medicine can be characterized as quickening, internal, and purifying in its effects on body processes, effects which are highly consistent with Shaker religious beliefs in active, physical worship, selflessness and spiritual purification by confession.     

Characteristics of bacterium GB-2, a presumptiveCytophaga species with novel immunoregulatory properties

A Gram-negative, psychrophilic bacterium, designated GB-2, was isolated from fetal calf serum and analyzed for its morphological, physiological, and biochemical characteristics. Gliding motility, sensitivity to actinomycin D, the presence of the pigment flexirubin and cytochrome c, growth on a variety of carbohydrates, the production of acid fermentation products, and a 34.9 mol% guanine+cytosine (G+C) content of bacterial DNA indicate GB-2 to be a member either of the generaCytophaga orFlexibacter. Growth of GB-2 was optimized in a simple defined medium to facilitate isolation and characterization of bacterial products. Liquid growth of GB-2 resulted in the release of significant quantities of a macromolecule free of both endotoxin and protein into the growth supernatant, which activated the proliferation of murine lymphocytes. The relationship between this bacterium and its end-products to other species of theCytophaga/Flexibacter group is discussed.     

The met-enkephalin analog FK 33-824 and naloxone do not directly influence cortisol secretion by cultured human adrenocortical cells

Systemic administration of the enkephalin analog FK 33.824 was previously shown to inhibit ACTH secretion in man. In this study, the direct action of this analog on cortisol release was studied. The enkephalin analog (1 uM and 10 uM) did not influence basal or ACTH-stimulated cortisol production by cultured isolated adrenocortical cells prepared from the hyperplastic adrenal glands from three patients with Cushing's disease. Naloxone (10 uM) had also no direct effect on cortisol release. It is concluded that the met-enkephalin analog used in this study and naloxone do affect the hypothalamo-pituitary-adrenal axis via a central effect.     

Genomic and cDNA clones of the homeotic locus Antennapedia in Drosophila.

Homeotic genes are involved in the control of developmental pathways: dominant mutations at the Antennapedia locus of Drosophila, for example, lead to replacement of the antennae on the head of the fly by mesothoracic legs. Using a combination of chromosome walking and jumping, we have cloned a DNA region from Drosophila containing Antennapedia. Five DNA inversion rearrangements which are associated with the Antennapedia mutant phenotype were localized within a 25-kb region. Genomic DNA sequences from this area were used as hybridization probes to screen cDNA libraries prepared from Drosophila embryonic and pupal poly(A)+ RNA. A 2.2-kb cDNA sequence (903) was isolated which appears to derive from at least four non-contiguous chromosomal regions that span 100 kb. It includes the positions of the inversion breakpoints. A second cDNA of 2.9 kb (909) is composed of sequences from at least three chromosomal regions, two of which are similar or identical to sequences contained in the 903 clone but the third is derived from genomic DNA within a putative 903 intron. The unusual size and complexity of this locus are discussed.     

Efficiency of Glasshouse Pot Experiments Rotating versus Stationary Benches

Pot cultures of rice (Oryza sativa L., var. Colusa) in flooded soil were used to measure comparative uniformity of growth where mutual shading was the primary source of variation. Data were analyzed according to various divisions of each layout into blocks, sections, and replicate pots to compare statistical efficiencies.