Prevention of bioterrorism by vaccines

Prevention against the weapons of bioterrorists is limited by the multiplicity of agents that could be used. Against smallpox, stocks of the classical vaccine must be prepared, but this vaccine is dangerous and we must look for a new and safer vaccine. A vaccine against anthrax is probably possible relatively soon. One may be less optimistic concerning plague, since it is not sure that we could protect against the pulmonary plague, but research in this field is an emergency. The large number of viruses capable of inducing haemorrhagic fevers makes especially difficult the preparation of vaccines against these infections. We must also make available monoclonal antibodies that could be used as therapies against toxin, notably botulism, or against antibiotic-resistant bacteria.     

Computer-aided hepatic tumour ablation: requirements and preliminary results

Surgical resection of hepatic tumours is not always possible, since it depends on different factors, among which their location inside the liver functional segments. Alternative techniques consist in local use of chemical or physical agents to destroy the tumour. Radio frequency and cryosurgical ablations are examples of such alternative techniques that may be performed percutaneously. This requires a precise localisation of the tumour placement during ablation. Computer-assisted surgery tools may be used in conjunction with these new ablation techniques to improve the therapeutic efficiency, whilst they benefit from minimal invasiveness. This paper introduces the principles of a system for computer-assisted hepatic tumour ablation and describes preliminary experiments focusing on data registration evaluation. To keep close to conventional protocols, we consider registration of pre-operative CT or MRI data to intra-operative echographic data.     

Travelling-wave analysis of a model of the immune response to cancer

In this paper we present a travelling-wave analysis of a mathematical model describing the growth of a solid tumour in the presence of an immune system response. From a modelling perspective, attention is focused upon the attack of tumour cells by tumour infiltrating cytotoxic lymphocytes (TICLs), in a small multicellular tumour, without necrosis and at some stage prior to (tumour-induced) angiogenesis. As we have shown in previous work, for a particular choice of parameters, the underlying reaction-diffusion-chemotaxis system of partial differential equations is able to simulate the well-documented phenomenon of cancer dormancy by depicting spatially heterogeneous tumour cell distributions that are characterized by a relatively small total number of tumour cells. This behaviour is consistent with several immunomorphological investigations. Moreover, the alteration of certain parameters of the model is enough to induce bifurcations into the system, which in turn result in tumour invasion in the form of a standard travelling wave. The work presented in this paper complements the bifurcation analysis undertaken by Matzavinos et al. [Math. Med. Biol. IMA 21 (2004) 1-34] and establishes the existence of travelling-wave solutions for the system under discussion by promoting the understanding of the geometry of an appropriate phase space.     

Evolutionary games with variable payoffs

Matrix games, defined by a set of strategies and a corresponding matrix of payoffs, are commonly used to model animal populations because they are both simple and generate meaningful results. It is generally assumed that payoffs are independent of time. However, the timing of contests in real populations may have a marked effect on the value of rewards. We consider matrix games where the payoffs are functions of time. Rules are found which hold in this more general situation, and the complexity of possible behaviour is underlined by demonstrating other conditions which do not hold and an illustrative game.     

The onset of Late Paleolithic in North China: An integrative review of the Shuidonggou site complex,China

Shuidonggou (SDG) attracts scholars who are interested in Late Paleolithic of China, even east Asia, from generation to generation since 1923 when rich lithic artifacts and animal fossils were discovered at locality 1. During the past almost one century, many excavations have been conducted by different institutes at different localities of SDG. Numerous data has been obtained and tens of thousands of artifacts were yielded. The understanding of nature and context of SDG is increasing gradually with the repeated excavation and in-depth research. The present paper reviewed the formal excavations and achievements in SDG. Especially, a series investigations and excavations since 2002 have been emphasized. After this long-term fieldwork, the geographic range of SDG has extended far beyond the range suggested by previous findings. The presence of discrete cultural horizons at various SDG localities indicate repeated use and occupation of the area by early human groups between 50–10 kya with a gap in LGM. During the repeated occupations, diverse and complex behaviors including gathering various plants, heat treatment preparation for knapping, making ornaments, engraving were identified using different kinds of methods and techniques by scholars. Paleoenvironmental reconstruction based on pollen analysis suggests that late Pleistocene/early Holocene human utilization of the SDG area occurred primarily around 32–24 kya and 13–11 kya when climatic conditions were more favorable. Years of excavations and researches make progress with nature of SDG. However, the issues about Initial Upper Paleolithic assemblages in SDG, origin/disappearance of Levallois-like technology in China are still open to debate. Further excavation and research at SDG1 will clarify these issues.     

Modification of HT 29 cell response to the vasoactive intestinal peptide (VIP) by membrane fluidization

We used liposomes made with phospholipids of fatty acid chain length ranging from C12:0 to C16:0 to modify the cAMP dependent protein kinase (PK) activity of HT 29 cells induced by VIP or forskolin. Both VIP and forskolin effects were inhibited in dilauroylphosphatidylcholine (DLPC) treated cells. PK activity was slightly lowered when cells were treated by dimyristoylphosphatidylcholine (DMPC) liposomes. However neither VIP nor forskolin-induced PK activities were affected with dipalmitoylphosphatidylcholine (DPPC) liposomes. Furthermore, the binding of [125I]VIP to DLPC treated cells was drastically lowered whereas no change was observed when cells were incubated with DMPC or DPPC liposomes. On the other hand, the interaction of HT 29 cells with DLPC vesicles provoked a decrease in membrane cholesterol content with subsequent increase in membrane fluidity. These findings provide evidence that, in HT 29 cells, the mechanisms of VIP-receptor interaction and of adenylate cyclase activation is lipid dependent and is regulated by membrane fluidity.     

Seuil thermique de développement de trois coccinelles prédatrices de la cochenille du manioc au congo

Résumé Le seuil thermique de développement de 3 prédateurs de la famille desCoccinellidae (un exotique et deux locaux) a été étudié. L'équation de la constante thermique a été utilisée pour le calcul du seuil thermique. Les données obtenues ont été comparées entre elles. L'espèce exotiqueHyperaspis raynevali a un seuil thermique de développement plus bas que celui des 2 espèces locales (Hyperaspis senegalensis hottentotta etExochomus flaviventris). Le seuil thermique suivant a été obtenu pour chaque espèce, à savoir: 11,81°C pourH. raynevali; 13,78°C pourH. s. hottentotta; 13,63°C pourE. flaviventris. Des différences de seuil thermique de développement et de mortalité ont été enregistrées entre le prédateur exotique et les espèces indigènes. Des hypothèses explicatives sont évoquées dans la discussion.      

Sterol-phospholipid interactions in model membranes Effect of polar group substitutions in the cholesterol side-chain at C20 and C22

The interactions of phospholipids with four different cholesterol derivatives substituted with one OH or one keto group at position C₂₀ or C₂₂ of the side-chain were studied. The derivatives were the 22,R-hydroxy; 22,S-hydroxy; 22-keto- and 20,S-hydroxycholesterol. Two aspects of the interactions were investigated: (1) the effect of the cholesterol derivatives on the gel → liquid crystalline phase transition of dipalmitoylphosphatidylcholine (DPPC) and of dielaidoylphosphatidylethanolamine (DEPE) monitored by differential scanning calorimetry and (2) The effect on the lamellar → hexagonal H_II phase transition of DEPE monitored by DSC and by ³¹P-NMR to determine structural changes. The gel → liquid crystalline phase transition was affected by the cholesterol derivatives to a much larger extent in the case of DPPC than of DEPE. In both cases, there was a differential effect of the four derivatives, the 22,R-hydroxycholesterol being the less effective. In DPPC-sterol 1:1 systems, 22,R-hydroxycholesterol does not suppress the melting transition, the ΔH values becomes 7.1 kcal · mol^?1 as compared to 8.2 kcal · mol^?1 for the pure lipid. 22,S-OH cholesterol has a much stronger effect (ΔH = 3.1 kcal · mol^?1) and 22-ketocholesterol suppresses the transition completely. In DEPE mixtures of all these compounds, the melting transition of the phospholipid is still observable. The transition temperature was shifted to lower values (?13.5°C in the presence of 20,S-OH cholesterol). The ΔH of the transition was lowered by these compounds except in DEPE-22,R-OH cholesterol mixtures and the cooperativity of the transition (reflected by the width at half peak height) was reduced. The lamellar → hexagonal H_II phase transition was also affected by the presence of these cholesterol derivatives. The transition temperature value was depressed with all these compounds. 20,S-OH cholesterol was the most effective followed by 22,R-OH cholesterol. The ΔH of the transition was not strongly affected. The molecular interfacial properties of these derivatives were studied by the monomolecular film technique. It is most likely that 22,R-OH cholesterol due to the hydroxyl groups at the 3β- and 22,R-positions orients with the sterol nucleus lying flat at the air/water interface, since the compression isotherm of either the pure sterol or the DOPC-sterol mixture (molar ration, 1:1) monomolecular film exhibits a transition at approx. 103 Ų, corresponding to the area of revolution of the sterol nucleus. This remarkable property, due probably to the existence of a kink between the side-chain and the long axis of the steroid nucleus, might explain the smaller effect of this sterol on the melting transition of either PC or PE systems.     

Torreites milovanovici Grubić, 1979, the first report of the Torreites genus in Iran

Late Cretaceous Torreites milovanovici, pertaining to Hippuritids (rudists) as marine heterodont bivalves, from SW Iran (northern Shiraz), is the centerpiece of this study. It is the first specimen of the Torreites genus recorded in Iran. More than 25 Torreites specimens were collected from the medium-bedded carbonate layer of the Upper Cretaceous succession of the study area. As well as in Iran, T. milovanovici specimens are recorded from Oman, and United Arab Emirates (UAE), although other species are found in Cuba, Jamaica, and Mexico. The Torreites-bearing bed is attributed to the clastic lower unit of the Tarbur Formation in Zagros Basin which is overlain by the carbonate upper unit of this Formation. Referring to field and laboratory observations as well as different previous references the Torreites-bearing carbonate layer in the study section can be ascribed to the Campanian. T. milovanovici specimens in Iran are compared with those recorded in Oman and UAE, using some determinative parameters. They show similarities in angles and size. Finding the species in a new area can be inspiring for future studies. It enhances the paleobiogeographical distribution of Family Torreitidae in the world and matching them chronologically can reveal some new evolutionary trends.     

Caractérisation d'une Mosaïque Forestière et de sa Dynamique en Forêt Tropicale Humide Sempervirente1

Using a 0.78 ha transect in an undisturbed forest in French Guiana, we sought a typology of forest mosaic units (5 × 5 m quadrats) based on diameter distribution with three main classes of trees ≥5 cm DBH. We identified nine basic structural types corresponding to potential stages of a sequence of development from colonization of gaps to filling of the vertical space among three layers. Two enumerations made over a 10-year interval (1981 and 1991), enabled a transition matrix to be estimated. This summarizes movement between structural types over the period and enables ideas on dynamics to be discussed.