Showing papers by "Institut national de la recherche agronomique published in 1971"

Time Horizon, Objective Function, and Uncertainty in a Multiperiod Model of Firm Growth

Abstract: The growing literature pertaining to multiperiod programming models of farm growth raises three problems that are ordinarily solved with makeshift solutions: the duration of time to be included within the planning horizon; the arbitrage between present and future consumption; and the introduction of uncertainty. The connections between these questions are shown. The net worth of the firm at the end of the planning horizon is maximized under the constraint of a linear consumption function. In this case it is possible to use the turnpike theorem and some additional theorems on separability of matrices to derive a simple rule for deciding on the appropriate length of planning horizon. The introduction of uncertainty shortens the practical planning horizon defined according to this rule.

The nutritive value of refined rapeseed oils: A review

Abstract: Recent findings on the nutritive value of rapeseed oil (RSO) with high erucic acid content have been compared to those of canbra oil (CO), an oil extracted from newly bred Canadian rapeseed with no erucic acid. Erucic acid in diets retards animal growth even if food consumption is not altered. Growth performances of CO are as good as olive or peanut oil. The unbalanced ratio of palmitic acid to monoethylenic acids of CO does not affect rat growth rate. Because of its glyceride structure and high content of erucic acid, RSO has a lower digestibility (81%) than CO (96%) in the rat. Unabsorbed erucic acid is not preferentially excreted as calcium soaps. Interesterification of RSO which converts 31.7% of the erucic chains to the 2 position improves digestibility of erucic acid. 2-Monoerucin is more efficiently absorbed than the free acid. In vivo metabolic conversion of erucic to oleic acid has been proved in the rat. β-oxidation of injected 14-14C labeled erucic acid proceeded at the same rate as oleic acid but the over-all yield of the reaction was lower. Fatty acid composition of tissues in animals fed RSO or CO is influenced on one hand by erucic and gadoleic (C20∶1) acids of RSO, and on the other hand by the unbalanced ratio of palmitic-monoethylenic acids and the linolenic acid content of both oils. Nonnegligible amounts of erucic acid are deposited in the body fats of rats, chickens, turkeys, lambs and found in the milk of female rats fed RSO. Almost no erucic acid is incorporated in liver and testicles in the rat and it is not recovered in chicken egg yolk. The effect of RSO on rat reproduction has been re-examined. Dietary lipid and vitamin levels are of great importance in the results obtained. RSO induces myocarditis in several animal species. Similar lesions, although less frequent and severe, have been observed also with CO in the rat. Some authors have reported that erucic acid of RSO was responsible for the effect on heart muscle. Common fatty acid patterns to both RSO and CO have to be further investigated to explain the persisting effect of CO.

Tubal surgery in the rabbit: Fertilization and polyspermy after resection of the isthmus

Abstract: Between January 1969 and September 1970 18 New Zealand white rabbits underwent laparotomy for isthmian resection. The contralateral tube remained intact to serve as a control. After mating autopsy revealed 11 ovulations on the anastomosed side. Eggs retieved from the control tube (79.3%) were proportionately greater in number than those recovered from the anastomosed tube (57.2%). 67% of the eggs from the anastomosed tube had been fertilized compared to 91% from the control tubes. 3 eggs from the anastomosed tubes of 3 animals were dispermic. It was concluded that normal fertilization and early cleavage of rabbit eggs may occur without the isthmus and that the isthmus exercises control over sperm transport to the site of fertilization.

Modification of the development of Beauveria tenella mycosis in Melolontha melolontha larvae, by means of reduced doses of organophosphorus insecticides.

Abstract: Infection experiments have been carried out in the laboratory by mixing increasing quantities of spores of Beauveria tenella and reduced doses of parathion or trichloronate (organophosphorus insecticides) with the rearing medium of white grubs (Melolontha melolontha) to verify whether it is possible to favour the development of the muscardine disease. The results are similar to those which were obtained previously with reduced doses of BHC: with low dosage of spores (5 × 104 per gram of peat) which does not produce the mycosis after 4 months at 20°C, the addition of small quantities of parathion or trichloronate gives a real increase of muscardine; with an inoculum of 1 × 106 spores per gram, the mortality by the fungus is approximately the same with or without addition of insecticide, but the development of the disease is more rapid in the case of a simultaneous contamination by the spores and one of the two insecticides. These results give the possibility of carrying out field experiments with low quantities of a non long lasting insecticide so as to favour the development of the muscardine disease in a natural population of white grubs. Resume MODIFICATIONS DU DEVELOPPEMENT DE LA MYCOSE A BEAUVERIA TENELLA DES LARVES DE MELOLONTHA MELOLONTHA AU MOYEN DE DOSES REDUITES D'INSECTICIDES ORGANO-PHOSPHORES Des experiences d'infection des larves de M. melolontha par le champignon entomopathogene Beauveria tenella, en presence de doses reduites d'insecticides organo-phosphores (parathion ou trichloronate), ont eTE realisees au laboratoire pour verifier s'il est ainsi possible de favoriser le developpement de la mycose. Les resultats confirment ceux obtenus anTErieurement avec des doses reduites de HCH: avec de faibles quantiTEs de spores (5 times 104 conidiospores par gramme de tourbe utilisee comme milieu d'elevage des vers blancs), qui a elles seules ne provoquent pas l'apparition de la maladie apres 4 mois d'observation a 20°, l'addition de faibles doses de parathion ou de trichloronate assure une reelle augmentation des cas de muscardine; avec un inoculum de 1 times 106 conidiospores par gramme, la mortaliTE par mycose est approximativement la meme avec ou sans addition d'insecticide, mais le developpement de l'infection est nettement plus rapide lorsque la tourbe est contaminee simultanement par le champignon et l'un des deux insecticides.

Epidémiologie de l’Enroulement de la Pomme de terre: capacité vectrice de stades et de formes des pucerons Aulacorthum solani Kltb. Macrosiphum euphorbiae Thomas et Myzus persicae Sulz

Abstract: L’etude comparee de la capacite vectrice de larves du 4e stade d’apteres, de nymphes des 3e et 4e stades d’ailes, d’adultes virginipares apteres et ailes d’une souche d’Aulacorthum solani, deMacrosiphum euphorbiae et deMyzus persicae a ete realisee surSolanum tuberosum var.Claudia. Il ressort que les categories les plus efficaces sont les nymphes et les adultes apteres d’A. solani et les larves du 4e stade d’apteres deM. euphorbiae et deM. persicae; les categories les moins efficaces sont respectivement les larves du 4e stade d’apteres d’A. solani, les nymphes deM. euphorbiae et les adultes ailes deM. persicae.

Artefacts au cours de la préparation de coupes de grains d'amidon. Etude par microscopie photonique et électronique†

Abstract: Artefacts During the Preparation of Sections of Starch Granules. Studies under Light and Electron Microscope. Dark bands which are usually observed in ultrathin sections of starch granules, „coloured” or not, have been considered by some authors as marking the presence of protidic substances, by others as artefacts of sectioning, on account of the diversity of their shapes and the frequency of their appearance. Examinations under light microscope show that this phenomenon appears effectively, during the sectioning of the inclusion block, when the ultrathin section of starch comes into contact with the surface of water in the collecting tank and then swells. The examination under electron microscope of ultrathin sections shadowed with gold, allows us to show that these dark bands are the consequence of surface folding of the cut starch grains. The measurements of electron density show that there are folds like S or double folds like S, and that electron transmission across the sample follows a logarithmic rule. A discussion leads to think that these artefacts are the consequence of a defective permeation of starch with the inclusion material and the result of starch water affinity. We must definitely leave out that dark bands should be a manifestation of protidic material.

Spécificité de la protéase neutre de Micrococcus caseolyticus

Abstract: The specificity of an exocellular neutral protease produced by Micrococcus caseolyticus has been investigated with amides, dipeptides mono-and di-substituted dipeptides and glucagon. This protease does not exhibit exopeptidase activity: it splits neither amides : Leu(NH2), Phe(NH2), Ala(NH2), Val(NH2), Ileu(NH2), nor Gly-Leu, Gly-Phe, Gly-Ala, nor Z-Gly-Leu, Z-Gly-Phe, Z-Gly-Phe, Z-Gly-Ala. There is no free amino acid in glucagon digests. Therefore this protease has to be considered as an endopeptidase. Moreover it splits neither AcTyrOEt or BzTyrOEt (chymotrypsin substrates) nor TosArgOMe or BzArgOEt (trypsin substrates). The results obtained with disubstituted dipeptides Z-Gly-X(NH2) indicate that the peptide bonds which are hydrolyzed by the neutral protease were those involving amino groups of hydrophobic amino acids (Phe, Leu, Ala, Val, Ileu but not Trp) or of tyrosine. The highest rate of hydrolysis was obtained with Z-Gly-Phe (NH2); it was 1.48 micromoles per minute per mg of protease at 37°C. The second residue (X′) involved in the bond by the carboxyl group in the series Z-X′-Phe(NH2) has also an important effect on enzymic activity. So the rates of hydrolysis (in micromoles per min per mg of protease, at 37°), were: 2.01 for Z-Ala-Phe(NH2), 1.48 for Z-Gly-Phe(NH2) 0.25 for Z-Leu-Phe(NH2), 0.146 for Z-Ser-Phe(NH2), 0.140 for Bz-Gly-Leu(NH2) and 0.122 for Z-Gly-Val(NH2). This specificity has been confirmed with glucagon. Peptide bonds in which phenylalanine, leucine or alanine are involved by their amino group are rapidly split. The M. caseolyticus neutral protease displays a substrate specificity which is similar to that found for Pseudomonas aeruginosa or Streptomyces griseus. Thus the hydrophobic nature of the specificity of the protease of M. caseolyticus is not as absolute as that for the megateriopeptidase of Bacillus megaterium.

Premières observations sur le rôle de la température au moment de la transmission de l’Enroulement parAulacorthum solani Kltb.Macrosiphum euphorbiae Thomas etMyzus persicae Sulz.

Abstract: Des transmissions de l’Enroulement ont ete realisees sur germes deClaudia a 6, 15 et 24°, a l’aide de pucerons appartenant aux especesA. solani, M. euphorbiae etM. persicae. Il ressort que la transmission est d’autant plus elevee que la temperature est plus forte, le taux de cette augmentation n’etant pas le meme pour les divers stades, formes, souches de pucerons. De plus dans le cas des nymphes, il y a reduction du pourcentage de transmission lorsqu’apres une temperature de transmission de 24°, on applique des temperatures de 6 ou 15°. Il y a augmentation quand on soumet les tubercules a 15 ou 24° apres une temperature de transmission de 6°.

A telocentric translocation responsible for variegation in Petunia

Abstract: Striped mutants of Petunia were isolated after γ-ray treatment of zygotes and from the progeny of a haploid plant. This striped phenotype appeared to be associated with a telocentric translocation in which one arm of chromosome I was transferred to the end of the long arm of chromosome II. The phenotype and the breeding behaviour of the striped plants are explained on the basis of a mechanism similar to the breakage-fusion-bridge cycle described earlier in maize endosperm. The translocation is marked by the dominant allele P1 responsible for the synthesis of petunidin in flowers. The locus of this gene is on chromosome I. There is evidence for non-homologous pairing at meiosis of a haploid plant of Petunia hybrida.

Normal and abnormal fertilization in mammals.

Abstract: The cytological aspects of mammalian fertilization are now well-known, and timing of the fertilization stages can be given at least for the rabbit, cow and sheep. However, the physico-chemical mechanisms of sperm-egg attachment and transformation of the sperm nucleus into a male pronucleus remain obscure. Capacitation includes at least two modifications of the rabbit spermatozoon: sensitization to a fertilizin-like substance and the making available of acrosomic enzymes. Abnormal fertilization occurs when: – more than one spermatozoon enters the egg and several male pronuclei develop (polyspermy); – the second meiotic division does not result in the emission of a second polar body, and two female pronuclei form instead (digyny); – meiotic chromosome disjunction is incomplete and leaves a female pronucleus in the egg carrying one chromosome too many or too few, because a pair of bivalents has not separated (trisomic or monosomic fertilization). In normal conditions the frequency of such anomalies remains very low, but it can increase significantly as the delay between ovulation and fertilization lengthens. There are important differences arising from the influence of ageing between one species and another: the cow egg is very resistant whereas rabbit and pig eggs are very sensitive. It is thought that the human egg may be sensitive, but experimental proof is lacking. In vitro fertilization experiments show that abnormal formation of the male pronucleus occurs when aged sperm fertilize either freshly-ovulated or aged eggs. When in vitro matured oocytes are fertilized, formation of the male pronucleus does not take place, although the other events of the fertilization process are quite normal.

Isolement et identification de 4 UDP‐trisaccharides dans la glande mammaire et le colostrum de brebis

Abstract: 4 UDP-trisaccharides present in the mammary gland and colostrum of the ewe were isolated and identified. The nucleotides, extracted by means of trichloracetic acid, were purified in the following way : 2 ion-exchange chromatographies on Dowex 1 (formate), filtration on Sephadex G-25, paper electrophoresis, pH 5, followed by paper chromatography in 3 different solvents. Using these fractionation techniques, 4 uridine derivatives (X1′, X2′, Y1′, Y2′,) with positive reaction to the Warren neuraminic acid test, were obtained. UDP-5′, which constitutes the nucleotidic part of the 4 derivatives, was defined more accurately after various acid or enzymatic analyses. The isolation of UDP-5′ was made by ionexchange or paper chromatography and the total and labile phosphate was estimated. The Warren positive substances released from X1′, X2′, Y1′, Y2′, by neuraminidase or mild acid hydrolysis were identified as N-glycolyl-neuraminic acid for the X1′, Y2′ nucleotides, and N-acetyl-neuraminic acid for the X2′, Y2′ nucleotides. The behaviour of asialylated nucleotides to ion-exchange and paper chromatography is described as well as that of asialylated oligosaccharides. The 4 asialylated oligosaccharides contain galactose and an N-acetyl-D-hexosamine, the latter being N-acetyl-D-glucosamine in the case of X1′ and X2′, and N-acetyl-D-galactosamine in the case of Y1′ and Y2′. Total analysis of UDP-oligosaccharides shows a 1:1:1:1 ratio between uridine, N-acetyl-D-hexosamine, galactose, and neuraminic acid. The 1-P-trisaccharides and the trisaccharides were identified after phosphodiesterase hydrolysis followed by phosphatase hydrolysis. The N-acetyl-D-hexosamine carried the reducing group (sodium borohydride). Some structural characteristics of the 4 nucleotides were determined using β-galactosidase, neuraminidase, periodate, and periodate borohydride. Two of the nucleotides contain N-acetyl-glucosamine and are identical to those previously isolated from the goat colostrum. As for the two others, containing N-acetyl-galactosamine and appearing as new trisaccharide nucleotides, we may, on the basis of the results obtained, suggest the following sequences: a) UDP-N-acetyl-D-galactosamine (31) D-galactose (62) N-acetyl-neuraminic acid; b) UDP-N-acetyl-D-galactosamine (31) D-galactose (62) N-glycolyl-neuraminic acid. The possible role of these new nucleotides is discussed.

Relationship between immune reactions and tolerance to viruses

Abstract: In this review we plan to define the different aspects of viral infections and the concept of immunological tolerance in an attempt to clarify the meaning of “tolerance to viruses.” Subsequently, we shall try to present a general scheme of the mechanism of latency in viral diseases. Finally, we shall discuss the problem of the immune response in the inapparent forms of viral diseases and, conversely, the role of the host immunological status in development of virus infection.

Utilisation du piégeage sexuel pour l‘étude du déplacement de l'alucite sitotroga cerealella. (lépidoptère: gelechiidae) vers les cultures de mais

Abstract: Apres avoir mis en evidence, par une experience preliminaire, l'efficacite du piegeage sexuel chez S. cerealella, en dehors de sa periode normale d'activite, l'auteur a utilise cette methode au cours des annees 1968, 1969 et 1970 pour preciser le cycle biologique de cette espece dans le Sud-Ouest de la France. A cette occasion, l'action de differents facteurs sur le rendement du piegeage sexuel a pu etre etudiee. Parmi les facteurs physiques, le plus important parait etre la luminosite: c'est au crepuscule, pendant une heure environ, que se font les captures. Parmi les facteurs biotiques, la presence de la plante-hote, le Mais, et le stade phenologique de celle-ci ont une action determinante sur le taux des captures: ces dernieres sont plus nombreuses a partir de la floraison mâle jusqu'a l'approche de la maturite des grains. Summary SEX TRAPPING AS A METHOD FOR STUDYING DISPERSAL OF SITOTROGA CEREALELLA TO MAIZE FIELDS In order to determine if sex trapping could be utilised as a method of studying the dispersal of S. cerealella, 120 males reared in the laboratory were released and caught in a sex trap containing 100 virgin females. This first experiment took place in April 1968, outside the normal period of insect activity in nature. During the 10 days following the male release, we caught, at dusk, 40 males in this sex trap (30% of the release). This method was later used to determine the life cycle of the Angoumois grain moth in South-West France. S. cerealella appears in late May and early June in nature. It appears to produce three generations a year. The first and the second would be passed either on maize in cribs or stores, or on other cultivated or wild Graminaceae; on the other hand, the third generation would be spent on ears of maize in the fields. Among the climatic factors which influence the trapping rates of males, daylight seems the most important. The males are trapped only at dusk and for a period of about one hour. Temperature, aerial-humidity, and wind are not negligible. The sex attractiveness of virgin females seems such as to draw males from considerable distances: an experiment with several sex traps, each containing 5 virgin females only, has proved that it was possible to trap males at several hundred metres from the release point. Among biotic factors excluding those pertaining to the insect itself, the host-plant seems to be the principal factor for the number of trapped males. The maize has a double effect by its mere presence and its phenological stage: continuous trapping from June to November by two sex traps on uncultivated fields and two other sex traps on maize fields gave respectively the following results: 393 and 6520 males. The experiment of trapping males after release in uncultivated areas and in corn fields gave the following results (% of males covered), for the three periods studied: July 9–13 whorl stage: 7.3% August 27–31 late tasseling and silking stage: 19.6% October 4–8 milking stage of kernels, maturity: 19.0%

Nématodes associés et parasites deBlastophagus destruens Woll. [Col. Scolytidae]

Abstract: Le parasitisme par Nematodes a ete etudie chez le ScolyteBlastophagus destruens, ravageur des Pins dans le Sud-Est de la France. Des especes deja connues de Nematodes associes a cet Insecte ont ete trouvees:Panagrolaimus tigrodonFuchs, 1930;Macrolaimus canadensisSanwal, 1960;Mikoletzkya sp etBursaphelenchus sp. Une espece nouvelle est decrite:Ruidosaphelenchus janasii. Les stades larvaires deParasitaphelencus papillatusFuchs, 1937 etParasitorhabditis piniperdae (Fuchs, 1937)Ruhm, 1954, vivent dans la cavite generale de l'hote. La variation des taux d'infection et l'action sur l'insecte hote de ces deux Nematodes parasites sont discutees.

Remarks on the acetic acid metabolism in yeast during sporulation

Abstract: We have noticed important metabolic modifications during the first 15 hours of the sporulation process of yeast in contact with acetic acid. Carbohydrate reserves, dry weight and proteins increase. On the other hand, the activity of fumarase and isocitritase in cell homogenates are hardly altered. The results prove true the hypothesis according to which the metabolism of acetic acid is altered during sporulation.

Relations entre l'état physiologique et l'aptitude à la sporulation chez la levure

Abstract: Cells harvested during logarithmic growth give a higher percentage of asci than cells harvested during stationary phase. This observation is valide whatever the carbon source. When the culture is done on yeast extract 0.5%, glucose 0.5%, the cells during logarithmic growth have a weak acetate QO2, a high endogenous QO2. The activities of fumarase and isocitritase are also weak. All these characteristics are not incompatible with an abundant sporulation.

Influence de la Composition Chimique du sol sur l'Utilité de l'Inoculation des Graines de Luzerne avecRhizobium meliloti

Abstract: Des essais au champ d'inoculation de la luzerne en France montrent que dans 10 a 20 pour cent des cas, le traitement accroit fortement le rendement. Une etude a ete entreprise pour voir ou l'inoculation de la luzerne doit etre recommandee.

Étude, par diffraction des rayons X, de I'influence de la cryodessiccation sur la structure cristalline de I'amidon

Abstract: Examination on the Influence of Freeze-Drying on Crystalline Starch Structure by Means of X-Ray Diffractometry. The influence of freeze-drying on the crystalline structure of various starches (potato, wheat, maize, waxy maize, manioca, arrow-root) and wheat amylose has been examined by means of X-ray diffractometric diagrams. Only the crystalline structure of potato starch is altered by the treatment. A change in structure becomes apparent only, if freeze-drying is done slowly and if the water content of starch is above 25%, related to d. s. However, a restoration of the original structure of starch is possible, by moistening under certain conditions as described in the text. An explanation for the observations is proposed by means of a new hypothesis on structure organization of starch granules as well as the part of water as a determining factor for organization.

Principes de la lutte microbiologique en agriculture

Abstract: L’experience acquise apres plus d’une decennie de developpement des recherches en pathologie des insectes permet de tenter d’etablir un premier bilan et de degager quelques principes a retenir pour l’application de la lutte microbiologique en agriculture. Ces principes decoulent, d’une part de nos connaissances sur les proprietes pathologiques et epizootiologiques des germes consideres, d’autre part des caracteristiques ecologiques des milieux concernes ainsi que des imperatifs agronomiques et economiques.1. Bases microbiologiques .C’est dans l’isolement et la caracterisation des differentes categories de pathogenes que les recherches ont ete les plus poussees. Elles ont abouti a une liste de plus d’un millier d’especes appartenant a tous les groupes : bacteries, rickettsies, virus, protozoaires, champignons, en negligeant les nematodes, parmi lesquelles seules deux bacteries, trois champignons et quelques virus ont fait l’objet d’experimentations.Les proprietes microbiologiques et les potentialites de ces 5 types de germe sont rappelees en insistant sur les aspects interessant la lutte microbiologique : virulence, specificite, remanence, facultes de conservation, possibilite de multiplication industrielle.2. Bases pathologiques .Le recours a l’arme microbiologique en defense des cultures est en fonction des donnees acquises sur les processus pathologiques determinant l’evolution des maladies de l’etat enzootique vers l’etat epizootique, apres intervention ou non de l’Homme. Ces phenomenes sont lies a la fois a l’agressivite du germe et a la receptivite de l’hote, mais aussi a l’action du milieu. Il est ainsi brievement discute du role respectif de la virulence des souches, de l’origine du pathogene (endemique ou introduit), de la biomasse des microorganismes d’une part, de la sensibilite de l’insecte d’autre part, qui peut dependre de son stade, de sa race, de la phase gradologique de la population ou de l’etat physiologique provoque par des desequilibres nutritionnels, des intoxications ou des troubles pathologiques, infections Chroniques ou latentes, maladies a enchainements.Dans cette « balance » entre le germe et l’hote, les facteurs du milieu ont une influence a la fois sur les deux populations antagonistes considerees isolement et sur leur interaction selon des phenomenes de « stress » dans lesquels les facteurs predisposants concernent l’hote alors que les facteurs activateurs agissent sur le microorganisme.3. Bases ecologiques .L’ideal de la lutte microbiologique est d’aboutir a l’introduction dans un ecosysteme d’un agent de regulation permanente du niveau de population du ravageur au-dessous du seuil de nuisibilite pour la culture consideree. Ce caractere de prevention a long terme implique de tenir compte non seulement de l’insecte a combattre et du germe a utiliser mais aussi de l’environnement dans lequel est effectuee la dispersion du pathogene. L’unite de surface pour les applications doit etre representative de cet environnement et constituer un ecosysteme autonome, elle est donc d’importance tres variable selon la formation vegetale consideree : foret, culture permanente, semi-permanente ou annuelle et selon la nature geographique du milieu.Dans ce contexte, les stations refuges ont une place privilegiee et, en milieu cultive, il ne faut pas negliger l’action des facons culturales et l’influence des rotations sur la, survie de l’hote et du pathogene. La persistance endemique de celui-ci est liee, en effet, au maintien d’une population minimum de sorte que, dans l’appreciation des resultats d’une application, la morbidite a plus d’importance que la mortalite.Le pathogene introduit entre en concurrence avec les autres agents biotiques de regulation de la population-hote (entomopha- ges, autres maladies), aussi son application doit etre faite lorsque la biologie de l’espece, le stade d’evolution du ravageur, l’etat gradologique de la population permettent d’esperer qu’il constituera un des « facteurs cles » dans la dynamique de cette population.Le traitement generalise par un microorganisme entraine une certaine pollution du milieu qu’il est preferable d’essayer d’eviter en ayant recours a des applications localisees.4. Bases agronomiques .Les connaissances du microbiologiste, les conditions du pathologiste et le point de vue de l’ecologiste ne sont pas toujours en accord avec les besoins de l’agronome. Ainsi la selectivite de l’arme microbiologique amene le plus souvent a inclure la preparation biologique dans un programme de lutte integree ; l’action epizootique a long terme est parfois incompatible avec la sauvegarde de la recolte, soit quantitativement en fonction du taux minimum de survie du ravageur et du seuil de tolerance de la culture, soit qualitativement en fonction des normes de commercialisation.Le type de culture est le facteur determinant pour le choix d’une technique de lutte. La foret constitue le milieu le plus favorable a la lutte microbiologique proprement dite, alors que dans les cultures annuelles, il n’est possible actuellement que de recourir a des traitements phytosanitaires selectifs, a l’aide par exemple de Bacillus thuringiensis ou de certains virus.

Expression of Antigenic Determinants and Virus Synthesis in Mammalian Cells

Abstract: Publisher Summary This chapter focuses on the expression of antigenic determinants and virus synthesis in mammalian cells. In vitro cultures have shown that in conditions where cellular metabolic processes have been repressed, dedifferentiation of the cells is slowed down; hence, an active metabolic turnover, not necessarily of a mitotic character, participates in the process of dedifferentiation. It has been shown that cells that otherwise dedifferentiate could be kept in a differentiated state for many cell generations by changing the nutritional and growth conditions of the cultures. The chapter explains the relationship between antigenic determinants and virus synthesis expression in mammalian cells, and shows that these two functions might regulate cell differentiation and oncogenesis. It elaborates spontaneous variations in antigenic and viral expressions, the effect of viral infection on the antigenic expression of the host cell, the regulatory mechanisms involved in antigenic and viral expression and their role in oncogenesis. It also describes the use of plasmocytoma cells as a model for studies on cell differentiation.

Die Entwicklung hochmolekularer Kohlenhydrate im Maiskorn während des Reifeprozesses

Abstract: Development of High molecular Carbohydrates during the Maturation of the Maize Kernel. The development of starch, pentosans and cellulose during the formation and the maturation of the maize kernel (variety INRA 260) grown on the same field during two succeding years has been examined. The results make possible to precise the proportion of these carbohydrates in regards to the total dry matter of the kernel at each moment of the maturation. Furthermore when the results are expressed on the 1000 kernel weight, the accumulation of the carbohydrates in the kernel becomes more evident. The results are not given as a function of the time of maturation, but as a function of a climatic factor, the daily mean temperature added up from flowering. This makes possible to distinguish certain important phases in the formation of the carbohydrates and to compare more easily the results of different years. Furthermore the influence of other climatic factors on this formation can be determined.

New Tendencies in Plant Protection

Abstract: Concern about pesticide residues and the unprofitability of classical treatments through secondary complications has led to a new approach to plant protection problems. Applications must be based on the assessment of their necessity and full account must be taken of the advantages offered by various possibilities of biological control (introduction of parasites or predators, their mass-breeding, genetical control, use of attractants) and other procedures (breeding for resistance, cultural measures). Close co-operation between the various sectors of research involved is recommended.