Role of the Photoperiod Preceding a Flower-Inductive Dark Period in Dark-Grown Seedlings of Pharbitis nil Choisy

Flowering responses to a single photoperiod, of various durationsand irradiances, followed by an inductive dark period were investigatedwith dark-grown seedlings of Pharbitis nil Choisy. The numberof flower buds induced in each plant (NFB) increased with theincrease of both duration and irradiance of the photoperiod.Reciprocity did not hold for this photoresponse within the rangeof 0-16 h and 2.5-10 W-m^-2, NFB depending on the duration ratherthan the irradiance. With lengthening of the dark period followinga photoperiod of 8 h or less, two different phases alternatelyappeared so that NFB sharply increased at 20-24 h and 40-43h after the onset of the photoperiod, then gradually decreased.When the photoperiod was longer than 8 h, NFB sharply increasedat 12–16 h after the end of the photoperiod and remainedaround the saturated value with longer dark periods. Far-redlight given immediately after the photoperiod inhibited flowering,the inhibitory effect being stronger the shorter the photoperiod.This far-red effect is mediated by phytochrome and P_FR seemsto be required during the inductive dark period following ashort photoperiod for floral induction. (Received December 23, 1983; Accepted April 12, 1984)     

Effect of High-intensity Light Given Prior to Low-temperature Treatment on the Long-day Flowering of Pharbitis nil

Pharbitis nil, strain Violet which had been exposed to high-intensitylight (18,000 lux at 23?C) for 7 days followed by a low-temperaturetreatment (13–14?C) for 7 days initiated flower buds evenunder continuous light, but plants given these treatments inreverse order failed to bud. Three days of high-intensity lightat 23?C was most effective in promoting the flower-inducingeffect of the subsequent low-temperature period. Six days oflow temperature following the 3-day high-intensity light periodinduced near-maximum flowering response. DCMU (5?10^–6M) given during the high-intensity light period inhibited flowering,but when given during or after the low-temperature period itwas ineffective. DCMU at the same concentration given before,during or after an inductive 16-hr dark period at 26?C did notinhibit flowering. Sucrose, ATP, NADPH and some other reducingagents tested did not nullify the DCMU effect nor substitutefor the effect of high-intensity light. But, the high-intensitylight effect could be substituted, at least partly, by 5-chlorosalicylicacid, 3,4-dichlorobenzoic acid and some other benzoic acid derivatives,which are highly effective in inducing long-day flowering inthe short-day plant, Lemna paucicostata. (Received October 20, 1981; Accepted February 3, 1982)     

Simple procedures for the rapid cleavage of ester lipids and for the large-scale isolation from brain of cerebroside sulfate

The ester groups of glycerophospholipids in tissue extracts can be cleaved in less than 10 min at room temperature if the lipids are extracted with hexane-isopropanol and the filtrate is treated with methanolic NaOH. The resulting mixture can be treated with aqueous Na-sulfate containing sulfuric acid and partitioned to remove the inorganic reagents and hydrophilic ester degradation products. When the procedure is applied to brain lipid extracts, the addition of alkali produces a second, lower phase that contains much of the hydroxycerebroside, virtually all of the sulfatide in the extract, and small amounts of other lipids. The sulfatide can be isolated from the lower phase by neutralizing it with HCl in aqueous methanol, and partitioning with chloroform to remove nonlipid components. The lower phase is evaporated to dryness and treated with periodic acid to convert the cerebroside to a less polar product. The lipids recovered from the reaction mixture are then fractionated with a Florisil column, which yields highly purified sulfatide. Starting with 300 g of pig brain one can obtain about 1.1 g of sulfatide in 4 working days, using conventional, compact equipment. Since the precipitation step is almost complete, and the procedure can be scaled down to very low levels, the method has promise for quantitation methods and isotopic studies of sulfatide metabolism.     

Effect of 7-fluoro prostacyclin,a stable prostacyclin analogue,on cAMP accumulation and prostaglandin binding in mastocytoma P-815 cells

The effect of 7-fluoro proscyclilin (PGI₂-F), a chemically stable analogue of prostacyclin, on cAMP accumulation in and [³H]PGE binding to mastocytoma P-815 cells was compared with those of the Na salt and methyl ester of prostacyclin (PGI₂Na or PGI₂Me), which are rapidly inactivated in aqueous solution or metabolized in the tissue.PGIF was as effective as PGI₂Me, and slightly less effective than PGI₂Na in stimulating cAMP accumulation in mastocytoma cells and rabbit platelets. PGI₂F was also more stable than PGI₂Me or PGI₂Na, and retained its original cAMP elevating activity even after incubation with or without cells for 4 h at 37°C. Cells which had been exposed to PGI₂F and then washed free of unbound reagent continued to produced cAMP for more than 3 h. PGI₂F was also as effective as PGE₁ or PGE₂ in displacing [³H]PGE₂ bound to the cells. Non-competitive inhibition by PGI₂F or PGI₂Me of [³H]PGE₂ binding to the cells, with apparent K_is of 1.29 μM and 1.13 μM, respectively, indicates the presence of different receptors for PGE₂ and for PGI₂F or PGI₂Me in mastocytoma P-815 cells.     

Translocation of colicin E1 through cytoplasmic membrane of Escherichia coli

The product of the malE—lacZ gene fusion was reported to compete with some proteins including outer membrane lipoprotein in the protein translocation across the Echerichia coli membrane. The fusion product also inhibited colicin E1 export. Furthermore, globomycin, which accumulated prolipoprotein in the membrane, inhibited the translocation of colicin E1 in the wild-type cells, but not in lipoprotein-negative mutant cells. Since colicin E1 contains the internal signal-like sequence [Proc. Natl. Acad. Sci. USA (1982) 79, 2827–2831], these results suggest that colicin E1 is exported by the aid of this sequence at a common site for maltose-binding protein and lipoprotein translocation.     

Glucans in the Cell Walls Regenerated from Vinca rosea Protoplasts

Protoplasts prepared from suspension-cultured Vinca rosea cellswere cultured for 5 days. The cell walls regenerated from theprotoplasts were mainly composed of glucans having 1,3- and1,4-linkages. To investigate the molecular species, these glucanswere separated into four fractions: EDTA (50 mM, pH 4.5)-soluble(fraction E), KOH (24%)- soluble but not precipitatable by neutralizationwith acetic acid (fraction K-S), KOH (24%)-soluble and precipitatableby neutralization with acetic acid (fraction K-P), and KOH (24%)-insoluble(fraction C). By means of sugar composition analysis, methylationanalysis, periodate oxidation and enzymatic digestion, the molecularspecies of the glucans contained in the regenerated cell wallswere deduced to be ß-1,4-glucan (cellulose) and ß-1,3-glucan.Fraction C was mainly composed of ß-1,4-glucan; ß-1,3-glucanwas mainly recovered in fraction K-P. The ß-l,3-glucanwas soluble in dilute alkali solution, but was only slightlysoluble in water. The ß-1,3-glucan had an essentiallyunbranched structure, and its weight average molecular weightestimated by gel permeation chromatography was 4.5–5.0x 10⁴. ¹ Present address: Division of Environmental Biology, NationalInstitute for Environmental Studies, Yatabe, Tsukuba, Ibaraki305, Japan (Received May 21, 1981; Accepted October 13, 1981)     

The “happy puppet” syndrome in two siblings

Summary Disomic and trisomic cells of a patient with Down syndrome mosaic were used to study the effect of the additional chromosome 21 against an identical genetic background. The frequency of Ag staining and the participation in satellite associations were determined for each pair of acrocentric chromosomes. The additional chromosome 21 of the trisomic cells and its homologues proved to be regularly Ag positive. Therefore the trisomic cells showed more Ag positive chromosomes and more satellite associations per cell than the diploid cells. Thus, no compensation for the additional rRNA-gene dose could be found in the cells of the trisomic line.