Antiprion action of new cyclodextrin analogues

Background

Prion disorders are characterised by the accumulation of a misfolded isoform (PrP^Sc) of the host encoded prion protein (PrP^C). This paper examines the antiprion potential of cyclodextrin (CD) analogues and it identifies sulphated-β-cyclodextrin, with a half-maximal inhibitory concentration (IC₅₀) of 2.4 μM, as having 31-fold greater antiprion activity than that previously reported for β-cyclodextrin (βCD).

Methods

Scrapie infected cells were treated with a range of βCD analogues. This enabled a CD structure to antiprion activity analysis to be carried out. The metachromatic activity of each of the cyclodextrins was determined, this test is employed to mimic complexation of glycosaminogylcans to a cell membrane.

Results

Sulphated-βCD had an IC₅₀ of 2.4 μM and it was the only CD found to have metachromatic activity. Its activity was equivalent to that of heparin and heparin sulphate, this may account for sulphated-βCD's superior antiprion action.

General significance

In solution heparin can form a helical structure with a hydrophobic interior, the hydrophobic interior of cyclic CDs is vital for CD molecule encapsulation. The controlled CD structure, however, restricts degradation by human enzymes; consequently sulphated-CDs could be ideal candidates in the search for prion therapeutics. Sulphated-CDs may open up avenues for the treatment of TSEs.     

Reef to basin sediment transport using Halimeda as a sediment tracer,Grand Cayman Island,West Indies

Fragments of the calcareous green alga Halimeda form a large part of the sediment in the fringing reef system and adjacent deep marine environments of Grand Cayman Island, West Indies. Nine species combine to form three depth-related assemblages that are characteristic of the major reef-related environments (lagoonpatch reef, reef terraces, and deep reef). These modern plant assemblages form the basis of the use of Halimeda as a sediment tracer. Halimeda-based tracer studies of Holocene sediments indicate that only sediments containing deep reef species of Halimeda are presently being transported through the reef system by sediment creep and being deposited at the juncture of the upper and lower island slope. Sediments containing shallow reef Halimeda are retained within the reef and lithified by marine carbonate cements. Tracer studies of Pleistocene sediment indicate large amounts of reef-derived carbonate sand containing deep water Halimeda were produced during interglacial high stands of sea level. Much of this material was removed by turbidity currents moving out of the reef system to the island slope down submarine channels perpendicular to the reef trend. These channels may still be identified on bathymetric profiles, but are no longer receiving coarse reef debris and are veneered with a blanket of pelagic carbonate mud.     

The changing estrogen content of the nuclear fraction of human myometrium during labor

The cytosol and nuclear fractions were prepared from 32 pieces of myometrlum obtained from 20 elective cesarean sections (regarded as typical of quiescent pregnancy (P)) and 12 emergency cesareans (performed after labor had started and therefore taken as typical of labor (L)). The nuclear fraction was purified by standard procedures. All protein-bound estrogen was released from the nuclear fractions, and the released estrogen simultaneously solubilized by denaturation with ethanol. The estriol (E₃) and estradiol (E₂) content of the alcohol solutions were assayed by radioimmunoassay with highly specific antisera for E₃ and E₂. In the L group, average E₃ content was slightly (not significantly) lower, and average E₂ content was significantly (P < 0.005) higher, than in the P group. The E₃/E₂ ratio decreased dramatically (P < 0.001) during this change from P to L.     

A tomato ER-type Ca-ATPase, LCA1, has a low thapsigargin-sensitivity and can transport manganese

Recombinant Ca²⁺-ATPase from tomato (i.e. LCA1 for Lycopersicon esculentum [Since the identification and naming of LCA1, the scientific name for the tomato has been changed to Solanum lycopersicum.] Ca-ATPase) was heterologously expressed in yeast for structure-function characterization. We investigate the differences between plant and animal Ca pumps utilizing comparisons between chicken and rabbit SERCA-type pumps with Arabidopsis (ECA1) and tomato plant (LCA1) Ca²⁺-ATPases. Enzyme function was confirmed by the ability of each Ca²⁺-ATPase to rescue K616 growth on EGTA-containing agar and directly via in vitro ATP hydrolysis. We found LCA1 to be ∼300-fold less sensitive to thapsigargin than animal SERCAs, whereas ECA1 was thapsigargin-resistant. LCA1 showed typical pharmacological sensitivities to cyclopiazonic acid, vanadate, and eosin, consistent with it being a P_IIA-type Ca²⁺-ATPase. Possible amino acid changes responsible for the reduced plant thapsigargin-sensitivity are discussed. We found that LCA1 also complemented K616 yeast growth in the presence of Mn²⁺, consistent with moving Mn²⁺ into the secretory pathway and functionally compensating for the lack of secretory pathway Ca-ATPases (SPCAs) in plants.     

A comparison between 3,5-diiodo-4-hydroxybenzoic acid and 2,3,5-triiodobenzoic acid. I. Effects on growth and gravireaction of maize roots

A comparison between the effects of DIHB and TIBA on growth and gravireaction of 15 mm primary maize ( Zea mays L. cv. LG 11) roots is presented. Intact roots were pretreated in the dark for 1 h with buffered solutions (pH 5.0 or 6.0) containing DIHB (10, 50, 100 μ M ). The plantlets were then maintained either vertically or horizontally in the dark or the light, and growth and gravireaction were recorded using a macrophotographic technique. Pretreatment with DIHB slightly inhibited growth and delayed gravireaction. These effects were most marked with DIHB at 100 μ M and were enhanced when DIHB was applied at pH 5.0. Similar effects were observed in roots pretreated with TIBA, but at a lower concentration (1 μ M ). The similarities between DIHB and TIBA as regards both chemical structure and the inhibition of gravireaction and growth, lead us to suggest that a major mode of action of DIHB, like TIBA, is the inhibition of indol-3yl-acetic acid transport.     

Intrinsic protein phosphorylation in synaptic plasma membrane fragments from the rat General characteristics and migration behaviour on polyacrylamide gels of the main phosphate acceptors

Preparations enriched in synaptic membrane fragments from rat cerebral cortex contain protein kinases which phosphorylate membrane proteins in reactions dependent on cAMP, Ca²⁺ (in the absence or presence of calmodulin) or independent of these factors. In these present work characteristics of the main phosphorylated acceptors were studied and compared with the results of other investigations. Apparent molecular weights were estimated by determining electrophoretic mobility on gels of different acrylamide concentration. Irregular migration behaviour was detected by measuring free mobilities from Ferguson plots. Certain phosphate acceptors were found to exhibit anomalously low free mobilities and it was concluded that estimates of molecular weight for these acceptors were unreliable.     

Phytoplankton distribution in a floodplain lake and river system. II Seasonal changes in the phytoplankton communities and their control by hydrology and nutrient availability

Phytoplankton community development and water chemistry werestudied for 2 years in the lowland R.Bure and most of the Broads(shallow lakes) associated with it. The data were analysed interms of ‘time for development’, which is the minimumestimated time that an average parcel of water takes to reacha site plus that it spends in it before it moves on downstream.This allows to some extent for the delaying effects that theBroads have on downriver water movement. Regressions of meanchlorophyll a on time for development were linear and suggestedthat the upstream Broads, where phytoplankton first developsin quantity in the system, have retained the water for longerthan anticipated from hydrological measurements. They effectivelyadded several weeks to the time for development. Available phosphateand nitrate concentrations decreased with time for development.Those for silicate increased. Seasonal changes in the upperpart of the study area were largely in centric diatom species.Pennate diatoms and cyanophytes became predominant in the lowerstretches. All major species were present at the extreme upperend of the stretch. With increasing development time, in a watermass dominated by water entering at the head of the study area,a succession of Cyclotella meneghiniana, Stephanodiscus hantzschiiand Melosira species was followed by Oscillatoria species thenDiatoma elongatum, Synedra ulna and Anabaena planctonica. Possiblereasons for these changes are discussed. Over 80 other taxawere present though none were so abundant as the above species.The succession is interpreted in terms of nutrient physiologyand algal growth rates to generate hypotheses for experimentaltesting.     

A logarithmic ratio amplifier and range expander for use with dual-beam colorimeters

Many early-model Technicon amino acid analyzers and Autoanalyzers are still in use. They lack, however, the sensitivity of current-model machines. the colorimeter design used in these machines employs a single light source which provides dual beams, a reference beam and a sample beam which pass to identical photovoltaic cells. The ratio of sample to the reference voltage is measured continously in a null balance system by the recorder. The design provides an extremely stable output which as such is amenable to range expansion. Nevertheless, a range expander and linear absorbance output unit is not readily available commercially.The present communication presents details of the design and performance of a logarithmic ratio amplifier and range expander for use with dual-beam colorimeters, as examplified by the Technicon system. The unit is simple and may be constructed by a nonspecialist in 2–3 days. The design chosen allows the use of low-cost components, thus keeping materials cost less than $75.