Heterogeneity of LSD-displacing factors and multiple types of high affinity LSD-binding sites

Heterogeneity of high affinity LSD-binding sites was confirmed by displacement studies with 2-bromo (+)—LSD and with apamin, a peptide neurotoxin. In line with the concept of multiple binding sites, a number of fractions of putative endogenous ligands could be separated from rat brain extract. The LSD-displacing β-fraction was not detectable in tissues lacking high affinity LSD-binding sites. High affinity dopamine- and serotonin-binding was differentially affected by the β-fraction.     

Uptake, transport and metabolism of cytokinin in moss protonema

Uptake, transport and metabolism of cytokinin in the protonemaof Funaria hygrometrica were studied using labelled kinetin(6-furfurylamino [8-¹⁴C]-purine). All cells of the protonema,chloronema and caulonema, were able to take up kinetin, whichwas carried in the symplastic transport system from cell tocell. Radioactivity was especially accumulated in growing cellsof the protonema. Kinetin was metabolized immediately afteruptake. While only very little kinetin (less than 1%) remainedas free kinetin and one part was immobilized in chromatographicseparation [e.g. attached to proteins and incorporated intonucleic acids (17)], most of the remaining kinetin was metabolizedto adenine derivatives. Exogenously supplied adenosine changedthe metabolism of kinetin. In the caulonema, adenosine reducedthe turnover of kinetin to other adenine derivatives and enhancedthe content of labelling in the start fraction. Thus adenosinecan stimulate cytokinin-dependent bud formation in moss protonema. (Received November 24, 1977; )     

New species of Roccellinastrum with an emendation of the genus

The genus Roccellinastrum Follm. emend. Henssen & Vobis is placed in the Lecideaceae. Two new species are described, R. epiphyllum Henssen & Vobis, from Chile and R. neglectum Henssen & Vobis, from New Zealand and Tasmania. The new combination R. candidum (Mull. Arg.) Henssen is proposed. Roccellinastrum is characterized by apothecia of diverse shape without a proper margin, and a developmental morphology corresponding to that of the Lecanorales, by small amyloid asci, branched paraphyses and excipular hyphae, a byssoid–spon–giose thallus composed of thick–walled hyphae, and members of the Chlorococcales as phycobionts. The principal chemical constituent is protocetraric acid. The species have different spore septation and chemistry. Summary in Spanish.     

Effect of cholesterol and dipalmitoyl phosphatidylcholine enrichment on the kinetics of Na−Li exchange of human erythrocytes

Summary The effects of cholesterol loading and depletion and of a 10% replacement of native phosphatidylcholine by dipalmitoyl phosphatidylcholine (di 16:0-PC) on kinetic properties of human red cell Na–Li exchange have been studied.Compared to control erythrocytes (cholesterol/phospholipid ratio (C/P=0.8–0.9)),V _max of phloretin-sensitive Li uptake and of Li efflux stimulated by extracellular Na (Na _o ) were reduced by 15–30% in cholesterol-loaded red cells (C/P=1.05–1.33). The apparentK _m values for external Li (Li _o ) and for internal Li (Li _i ) were decreased by about one-third in these cells. Cholesterol depletion (C/P=0.7) exerted opposite effects on the kinetics of Na _o -dependent Li efflux. On augmentingC/P from 0.66 to 1.0,V _max of Na _o -dependent Li efflux was reduced by about 30%; increasingC/P above 1.0 caused no further lowering ofV _max. Li leakage rates monotonically decreased over the whole range ofC/P ratios examined (0.66–1.3). This indicates that Na–Li exchange and Li leak are differentially affected by cholesterol.Incorporation of di 16:0-PC (replacement of 3% of total red cell phospholipids) caused similar kinetic alterations of Na–Li exchange as a rise in membrane cholesterol by 20–50%. Notably, selective incorporation of di 16:0-PC into the outer monolayer increased both intra- and extracellular Li binding affinities of Na–Li exchange and lowered its maximum velocity. Thus, both di 16:0-PC enrichment and cholesterol loading exerted an uncompetitive type of transport inhibition. The results are in agreement with the hypothesis that the kinetic alterations of red cell Na–Li exchange seen in a subgroup of essential hypertensive patients could be due to subtle changes in the molecular species composition of individual phospholipids.     

Measurements of pH in the apoplast of sunflower leaves by means of fluorescence

A method was elaborated by which the pH in leaf apoplast can be measured. The technique is based on the pH dependent fluorescence of 5-carboxyfluorescein (5-CF) or fluorescein isothiocyanate (FITC). The fluorescein isothiocyanate is coupled with a macromolecular dextran molecule (FITC-dextran). For eliminating the effect of the absolute dye concentration the dual excitation technique was applied. It was shown that the ratio of fluorescence excited by light of 491 nm and 463 nm was virtually independent of the concentration of 5-CF and that this fluorescence ratio was related to the pH. The plasmalemma is practically impermeable to FITC-dextran and in the test we carried out over a period of 6 h not the slightest indication was found that it may penetrate the plasma membrane. For 5-CF this cannot be ruled out completely. It is possible that at pH values below 4.5 it may penetrate biological membranes at low rates.
Experiments with leaves of sunflower ( Helianthus animus cv. Erika) perfused with 5-carboxyfluorescein and supplied with different nitrogen forms showed that NH⁺₄ application resulted in a decrease and NO⁺₃ application in an increase of the leaf apoplast pH. Leaf spraying with fasicoccin was followed by a pH decrease, while leaf spraying with the protonophores p -trifluoromethoxy carbonytcyanide phenylhydra-zon (FCCP) or nigericin resulted in neutral apoplastic pH. These results provide evidence that the method is well suited for measuring the response of the leaf apoplast pH to changing physiological conditions.     

Evidence for a driving role of ingrowing axons for the shifting of older retinal terminals in the tectum of fish

In amphibians and teleosts, retina and tectum grow incongruently. In order to maintain the retinotopy of the retinotectal projection, Gaze, Keating, and Chung (1974) postulated a shifting of terminals throughout growth. In order to test the possibility that ingrowing retinal fibers are the driving force for this shifting, we induced a permanent retinal projection into the ipsilateral tectum in juveniles of the cichlid fish Haplochromis burtoni. The surface of the tectum had increased (11–18 months later) 2.5–5.8 times, and the surface of the retina 8.6–14 times. Filling of ganglion cells with horseradish peroxidase (HRP) retrogradely from the tectum showed ipsilaterally regenerating ganglion cells only in the center of the retina. The position of ganglion cells indicated that the ipsilateral projection derived only from axotomized and regenerating retinal ganglion cells but not from those newly born. Ipsilaterally projecting retinal fibers showed terminals only in the rostral half of the tectum. Comparison of area of terminations of ipsilaterally projecting ganglion cells at various times after the crush provided no evidence for expansion or a shift into caudal tectal areas throughout the period of growth. These findings are compatible with the idea that newly ingrowing fibers induce older terminals to move caudally.     

Separation of dissociated thyroid follicular and parfollicular cells: association of serotonin binding protein with parafollicular cells

Parafollicular cells (PC) of the sheep thyroid gland are neural crest derivatives that synthesize and release the biogenic amine serotonin (5-HT) as well as the hormone calcitonin. The thyroid also contains a highly specific serotonin-binding protein (SBP). Separation of dissociated thyroid cells was done to study the cellular localization of SBP and to develop a means of isolating PC for study. Various methods were used to obtain an enriched and purified population of PC. Minced thyroid glands were enzymatically dissociated and the cells were layered on a Ficoll linear density gradient. Fractions obtained from the gradient were examined for cell number, viability, 5-HT concentration, SBP activity, and morphology by electron microscopy. One of the fractions was found to be enriched in PC. High levels of 5-HT and SBP were also found in this fraction, whereas these levels were low where the majority of cells were found. This PC-rich fraction, however, contained numerous follicular cells (FC); therefore, additional approaches to cell separation were used. FC can be stimulated in vitro with thyroid stimulating hormone (TSH) to become intensely phagocytic. When stimulated cells were incubated in the presence of silica microspheres, the FC engulfed the microspheres, which were toxic to them. PC did not become phagocytic and were unharmed by the microspheres. Suspended cells, after incubation with microspheres, were centrifuged on a discontinuous gradient, and a PC-rich fraction was obtained. Silica, however, interfered with analysis of SBP. Another method to take advantage of the phagocytic potential of FC was therefore used. TSH-stimulated cell suspensions were passed through a column of sepharose to which thyroglobulin had been coupled. Stimulated FC apparently adhered to the beads and were retained by the columns. Fractions eluting from the columns were greatly enriched with PC. These fractions contained high levels of 5-HT and SBP, and considerably reduced FC contamination was found by quantitative electron microscopy. It is concluded that SBP is localized to PC in the sheep thyroid. The idea that these cells resemble serotonergic neurons in their mechanisms of 5-HT storage is supported.