Electron probe microanalysis of pyroantimonate precipitates in the cilia ofParamecium

Summary Electron-dense deposits were observed at the bases of the cilia ofParamecium fixed in 1% OsO₄ solution containing 2% potassium pyroantimonate. The deposits were shown to contain Ca and Sb by X-ray microanalyzer.     

A reinvestigation of the chemistry of the Dufours gland of the formicine ant,Anoplolepis custodiens

The components of individual Dufours glands excised fromAnoplolepis custodiens workers were analysed by GC-MS. In addition to then-alkanes andn-alkenes previously reported² in these glands, primary alcohols (C₁₉-C₂₂), secondary alcohols (C₂₀-C₂₃), 2-ketones (C₂₀-C₂₃) and possibly carboxylate ethyl esters (C₁₉ and C₂₁) were identified as components of these glands. It seems possible that these high-boiling compounds are used by the workers in laying trails on the hot sandy surfaces of their characteristic habitat and in lining of the inner walls of nests, but no standard compounds have been available to us for any behavioral studies.     

New contribution to the study of chromosomes of the European Cryptocephalinae (Coleoptera,Chrysomelidae)

Summary The chromosomes of three species ofPachybrachis and nine ofCryptocephalus chrysomelids were analyzed. The male meiotic bivalent formula ofP. azureus Suffr.,P. catalonicus Burl. andP. petitpierrei Daccordi is 7^II+Xy_r.Cryptocephalus sexmaculatus Ol. andC. vittula Suffr. have 13^II+Xy_p,C. bipunctatus L. 14^II+Xy_r,C. ochroleucus Steph. andC. ocellatus Drap. 14^II+Xy_p,C. crassus 01. 15^II+Xy_r,C. sulphureus 01. 15^II+Xy_p, the same number as inC. fulvus Goeze with 2n=32 chromosomes, whileC. primarius Har. has 19^II+Xy_p. The modal chromosome number inCryptocephalus is 2n=30 (about 60% of spp.), and most species are characterized their small chromosomes. The low variation found in the karyotypes of Cryptocephalinae along with their possible interrelationships with allied chrysomelid subfamilies are also discussed.     

Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat

Summary Hypothalamic tyrosine hydroxylase (TH) activity of castrate rats is modulated by testosterone propionate (TP) in vivo. Kinetic studies revealed that bothV _max andK _m were virtually unaltered for substrate tyrosine in the presence of an excess of DMPH₄ cofactor. TP replacement to castrate rats increased theK _m for added DMPH₄ cofactor, whileV _max decreased. These results suggest that TP decreases TH activity of castrate rats by inhibiting the enzymereduced pteridine cofactor complex.     

On the usefulness of macroeconomic forecasts as inputs to forecasting models

A forecasting model for y_t based on its relationship to exogenous variables (e.g. x?_t) must use x?_t, the forecast of x?_t. An example is given where commercially available x?_t's are sufficiently inaccurate that a univariate model for y_t appears preferable. For a variety of types of models inclusion of an exogenous variable x?_t is shown to worsen the y_t forecasts whenever x?_t must itself be forecast by x?_t and MSE (x?_t) > Var (x?_t). Tests with forecasts from a variety of sources indicate that, with a few notable exceptions, MSE (x?_t) > Var (x?_t) is common for macroeconomic forecasts more than a quarter or two ahead. Thus, either:

• (a) available medium range forecasts for many macroeconomic variables (e.g. the GNP growth rate) are not an improvement over the sample mean (so that such variables are not useful explanatory variables in forecasting models), and/or
• (b) the suboptimization involved in directly replacing x?_t by x?_t is a luxury that we cannot afford.

     

Ligand recognition by the I domain-containing integrins

Seven of the integrin α subunits described to date, α ₁ , α ₂ , α _L , α _X , α _d , α _M and α _E , contain a highly conserved I (or A) domain of approximately 200 amino acid residues inserted near the amino-terminus of the subunit. As the result of a variety of independent experimental approaches, a large body of data has recently accumulated that indicates that the I domains are independent, autonomously folding domains capable of directly binding ligands that play a necessary and important role in ligand binding by the intact integrins. Recent crystallographic studies have elucidated the structures of recombinant α _M and α _L I domains and also delineated a novel divalent cation-binding motif within the I domains (metal ion-dependent adhesion site, MIDAS) that appears to mediate the divalent cation binding of the I domains and the I domain-containing integrins to their ligands.     

Forecasting for the generation of trading signals in financial markets

In this paper we show that optimal trading results can be achieved if we can forecast a key summary statistic of future prices. Consider the following optimization problem. Let the return r_i (over time i=1, 2, ..., n) for the ith day be given and the investor has to make investment decision d_i on the ith day with d_i=1 representing a ‘long' position and d_i=0 a ‘neutral' position. The investment return is given by r=Σⁿ_i=1r_id_i−cΣⁿ⁺¹_i=1∣d_i−d_i−1∣, where c is the transaction cost. The mathematical programming problem of choosing d₁, ..., d_n to maximize r under a given transaction cost c is shown to have an analytic solution, which is a function of a key summary statistic called the largest change before reversal. The largest change before reversal is recommended to be used as an output in a neural network for the generation of trading signals. When neural network forecasting is applied to a dataset of Hang Seng Index Futures Contract traded in Hong Kong, it is shown that forecasting the largest change before reversal outperforms the k‐step‐ahead forecast in achieving higher trading profits. Copyright © 2000 John Wiley & Sons, Ltd.     

CSTX-9, a toxic peptide from the spider Cupiennius salei: amino acid sequence, disulphide bridge pattern and comparison with other spider toxins containing the cystine knot structure

CSTX-9 (68 residues, 7530.9 Da) is one of the most abundant toxic polypeptides in the venom of the wandering spider Cupiennius salei. The amino acid sequence was determined by Edman degradation using reduced and alkylated CSTX-9 and peptides generated by cleavages with endoproteinase Asp-N and trypsin, respectively. Sequence comparison with CSTX-1, the most abundant and the most toxic polypeptide in the crude spider venom, revealed a high degree of similarity (53% identity). By means of limited proteolysis with immobilised trypsin and RP-HPLC, the cystine-containing peptides of CSTX-9 were isolated and the disulphide bridges were assigned by amino acid analysis, Edman degradation and nanospray tandem mass spectrometry. The four disulphide bonds present in CSTX-9 are arranged in the following pattern: 1-4, 2-5, 3-8 and 6-7 (Cys₆-Cys₂₁, Cys₁₃-Cys₃₀, Cys₂₀-Cys₄₈, Cys₃₂-Cys₄₆). Sequence comparison of CSTX-1 with CSTX-9 clearly indicates the same disulphide bridge pattern, which is also found in other spider polypeptide toxins, e.g. agatoxins (ω-AGA-IVA, ω-AGA-IVB, μ-AGA-I and μ-AGA-VI) from Agelenopsis aperta, SNX-325 from Segestria florentina and curtatoxins (CT-I, CT-II and CT-III) from Hololena curta. CSTX-1/CSTX-9 belong to the family of ion channel toxins containing the inhibitor cystine knot structural motif. CSTX-9, lacking the lysine-rich C-terminal tail of CSTX-1, exhibits a ninefold lower toxicity to Drosophila melanogaster than CSTX-1. This is in accordance with previous observations of CSTX-2a and CSTX-2b, two truncated forms of CSTX-1 which, like CSTX-9, also lack the C-terminal lysine-rich tail. Received 23 July 2001; accepted 31 July 2001     

Application of the linear partial information model to forecasting the Swiss timber market

Most often, statistical analyses only provide partial information about the appropriateness of different models, structures and parameters which may underlie the dynamic process that has generated a time series. Linear partial information (LPI), in particular, consists of linear restrictions such as LPI: p_a> p_b, p_a> p_c where p_a denotes the probability that structure a holds. Fuzzy information of this type can be put to use for decision-making by LPI analysis. In this paper, LPI analysis is applied to answer the question of whether subsidizing price, given an abnormal disturbance on the timber market, would contribute to continuous forest management, a stated goal of Swiss environmental policy.     

A new interpretation of the sex determining mechanism of the European earwig,Forficula auricularia

Riassunto Osservazioni su femmine diForficula auricularia L. indicano che esse possiedono un solo cariotipo formato da 22 autosomi e da 2 cromosomiX. Sulla base di questo studio, suggeriamo che i maschi con 3 cromosomi sessuali sono del tipoXYY, e nonXXY come precedentemente ritenuto da varii autori. Ci sono maschiXY ₁t, XY₂, XY₂Y₂ e mosaiciXY ₂/XY₂Y₂ nella popolazione. Inoltre viene dimostrato che solamente il più grande dei due cromosomi Y, che caratterizzano questa specie, viene accumulato nei maschi con un meccanismo multiple di cromosomi sessuali.

---

---

Supported by a postgraduate award from the Commonwealth of Australia to G.C.W. and by Public Health Service Grant No. GM-07212 from the Division of General Medical Sciences, U.S. National Institutes of Health and by a grant from the Australian Research Grants Committee.     

Physical characteristics of the cerebral big prothoracicotropic hormone fromManduca sexta

The prothoracicotropic hormones (PTTHs) are cerebral peptides that control insect postembryonic development by stimulating the prothoracic glands to synthesize ecdysteroids. InManduca sexta, the tobacco hornworm, two classes of PTTH are distinguished by their M_r, small (ca. 7 kDa) and big PTTH (ca. 25–30 kDa). Little is known about the physical nature of the PTTHs and this study takes a first step towards defining characteristics of theManduca big PTTH. The neurohormone has a Stokes radius of 2.59 nm and a sedimentation coefficient of 2.76 S. Based on these data, an M_r of 29,443.7 and anf/f ₀ of 1.27 were calculated. Combined, the physical data revealManduca big PTTH is an asymmetrical acidic homodimeric peptide with intra- and intermolecular disulfide bonds.     

Glycerol monoethers in the scent gland secretions of the western diamondback rattlesnake (Crotalus atrox; Serpentes,Crotalinae)

Summary 1-O-Monoalkylglycerols with C₁₂ to C₂₀ chains were identified in the scent, gland secretions of the western diamondback rattlesnake (Crotalus atrox). This is the first documentation of these compounds in the skin secretions of a reptile.     

Alkyl substituents and the cyclisation of esters

Summary K(CdCl₃) has a structure of the E 2₄-type. In comparison with the isotype (NH₄) (CdCl₃) only two of the three lattice constants have noticeably different values. They area andb which show a contraction of about 2%, whereas the constantc is about the same for both salts.     

Polarographic determination of the reaction rate of the second step in an SN1 displacement

Zusammenfassung Die Zeitabhängigkeit des polarographischen Stromes, welche man bei der gemäss SN1 verlaufenden Hydrolyse vonp-Methoxy-2-phenylpropylchlorid beobachtet, ermöglicht die Bestimmung der Geschwindigkeitskonstantenk ₁ der Gesamtreaktion sowie auch der Geschwindigkeitskonstantenk ₂ des zweiten raschen Schrittes, welcher nach pseudo-erster Ordnung verläuft. Fürk ₂ ergibt sich in Aceton, das 5% Wasser enthält, bei 25°Ck ₂=2,0×10³ sec^–1.

---

---

We would like to thank the N.R.C. for provision of a grant to purchase the Electrochemical System and the University of New Brunswick for a Fellowship for one of us (D.B.).     

An increase in the influx of calcium ions into cilia induces thigmotaxis inParamecium caudatum

To understand the role of calcium ions in thigmotaxis inParamecium caudatum, the effects of caffeine, ruthenium red and lanthanum (LaCl₃) on thigmotaxis were examined. Thigmotaxis in the CNR mutant, which lacks voltage-dependent Ca²⁺-channels in the ciliary membrane, was also examined. Ruthenium red and LaCl₃ suppressed thigmotaxis inP. caudatum, while caffeine enhanced it. The CNR mutant showed hardly any thigmotaxis. It can be thought that an increase in Ca²⁺ influx and the intraciliary concentration of Ca²⁺ ions induces thigmotaxis inParamecium.     

On the synthesis of serine and homoserine samples asymmetrically labelled with tritium and deuterium in the hydroxymethylene group

Summary (1 R) [1-³H,²H₁] 3-Phenylpropanol, the key intermediate in the synthesis of (4 R) [4-³H,²H₁] D, L-homoserine and of the (4 S)-isomer, is obtained from (1 S) [1-²H₁] 3-phenylpropanol and (1 RS) [1-³H] ethanol upon incubation with yeast alcohol dehydrogenase and NAD⁺; under similar conditions 2-phenylethanol undergoes very small exchange with [1-²H₂] ethanol.     

Ventilatory responses to CO2 at different body temperatures in the snake,Coluber constrictor

Summary Ventilatory responses to CO₂ were examined at different temperatures in the snake,Coluber constrictor. CO₂ sensitivity increased between 15 and 25°C but not between 25 and 35°C. A rapidly occurring off-CO₂ transient hyperpnea suggested the presence of an intrapulmonary chemoreceptor.     

Is ATP synthesized by a vacuolar-ATPase in the extremely halophilic bacteria?

The proton-dependent synthesis of ATP was demonstrated in representative members of the generaHalobacterium, Haloarcula, andHaloferax. In all cases, synthesis was not inhibited by nitrate or N-ethylmaleimide, inhibitors of the vacuolar-like ATPase found in Archaea, but was affected by azide, an inhibitor of F₀F₁-ATP syntheses. These observations extend the earlier observations withHalobacterium saccharovorum and suggest that ATP synthesis in these organisms is brought about by an F₀F₁-APT synthase.     

A marine mollusc provides the first example of in vivo storage of prostaglandins: Prostaglandin-1,15-lactones

Summary Prostaglandin-(PG) 1,15-lactones and, in smaller amounts, free acids, were isolated from both the mantle and the dorso-lateral appendices of the opisthobranch molluscTethys fimbria. In vivo conversion of PGs into the corresponding lactones and accumulation of PGE₂- and PGE₃-1,15-lactones in the appendages were shown. The detachment of these appendages from the molested mollusc caused the in vivo conversion of PGE₂- and PGE₃-lactones back to PGE₂ and PGE₃ respectively, thus providing the first example of a mechanism by which prostaglandins can be stored and, when needed, released.     

Influence of hydroxyurea,ellman's reagent and potassium ferricyanide on the radiosensitivity ofEscherichia coli

Zusammenfassung Zwei thiolbindende Agentien, K₃Fe(CN)₆ undEllmans Reagens wie auch der die DNA-Synthese hemmende Oxyharnstoff wurden als mögliche bakterielle Sensibilisatoren für Röntgenstrahlen untersucht. K₃Fe(CN)₆ und Oxyharnstoff im Medium können die Bakterien für die Inaktivierung durch Röntgenstrahlen besonders sensibilisieren (stärker mitE. coli B/r als mitE. coli B _s-1).