Orientation and ingestion rates of larval Anopheles albimanus in response to floating particles

Response of fourth-instar larvae of Anopheles albimanus Wiedemann (Diptera: Culicidae) to food and inert particles floating at the water surface was studied. In a choice test, larvae aggregated at powdered organic materials (blood meal, liver powder alfalfa flour and wheat flour) but not at inert materials (kaolin, chalk or charcoal). Larvae responded positively to proteins as well as some carbohydrates, but not to cellulose. Retention of larvae at food sources found by random locomotion was found to be responsible for larval aggregation. Larvae ingested food particles 6–9 times faster than insert particles. The significance of Anopheline feeding behavior in the development of formulations of stomach toxins (bacterial agents) used in larval control is discussed.

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Zusammenfassung Die vorliegende Studie befasst sich mit Verhaltensreaktionen von Anopheles albimanus Viertlarven auf an der Wasseroberfläche schwimmende Partikel. Verteilung und Orientierung der Larven wurde in einer Wahlapparatur quantifiziert. Nach Auftrag von Alfalfamehl, Weizenmehl, Stärke, Blutmehl, Leberpulver und Fischmehl wurde Aggregation der Larven in den beköderten Fächern der Apparatur beobachtet. Sowohl Proteine (Casein) als auch einige Kohlehydrate (Amylose, Amylopectin) lösten Aggregationen der Larven aus. Im Unterschied dazu führte Auftrag von Kreide, Kaolin, Polyaethylenpulver, Talcum oder Cellulose nicht zu Aggregationen. Zur Beschreibung der Entstehung larvaler Aggregationen bei Futterstoffen wurden die Schwimmbewegungen der Larven in Anwesenheit von Weizenmehl als Ködersubstanz quantifiziert. Da keine Attraktion der Larven im Sinne einer gerichteten Schwimmbewegung beobachtet werden konnte, wird geschlussfolgert, dass sofortige Beendung der Suchaktivität der Larven bei zufällig gefundenen Futterquellen für die beobachteten Aggregationen bei organischen Substanzen verantwortlich ist.Die Fressraten der Larven bei Angebot verschiedener Substanzen im Überschuss wurde bestimmt. Larven fülten drei von insgesamt sechs Darmabschnitten innerhalb von 15–30 min bei Angebot von Futtersubstanzen, während die Füllung von nur zwei Darmabschnitten mit inerten Materialien erst nach 90–120 min zu beobachten war. Die Resultate werden in Bezug auf wasseroberflächengebundene Formulierungen von Frassgiften diskutiert. Inerte Trägersubstanzen werden wahrscheinlich wesentlich langsamer aufgenommen als Futtersubstanzen. Da An. albimanus Larven nicht von Futterquellen angezogen werden, ist eine rasche und wirksame Giftaufnahme besonders dann zu erwarten, wenn die gesamte Oberfläche der Brutgewässer mit toxinhaltigen Trägerpartikeln bedeckt werden kann.

     

Fragile sites,chromosome evolution,and human neoplasia

Summary In a study of the possible relationship between human fragile sites, chromosomal rearrangements related to neoplasia, and chromosome regions involved in evolutionary changes, we have found that 17 fragile sites related to cancer, 15 fragile sites not related to cancer, and 17 non-fragile regions also related to human malignancy correspond or are close to bands involved in rearrangements that have taken place during chromosomal evolution in primates.     

Microfungus-yeast mixed cultures in the degradation of amylaceous wastes. II: An experimental design for optimization of yeast production

Summary By means of an experimental factorial design the role of several culture conditions is described and its values determined for the maximum yeast production in mixed cultures ofAspergillus oryzae andRhodotorula glutinis.     

Lipid accumulation inRhodotorula glutinis on sugar cane molasses in single-stage continuous culture

Microbial lipids produced byRhodotorula glutinis grown in continuous culture with molasses under nitrogen-limiting conditions were evaluated and the effects of growth rate on fatty acid composition were studied. As the growth rate decreased, cell biomass, lipid content and lipid yield gradually increased. The maximum lipid content recorded was 39% (w/w) of dry cell biomass at a dilution rate of 0.04 h^–1. The growth rate also affected fatty acid composition: oleic acid decreased with decreasing growth rate while stearic acid increased.     

Studies of oligonucleotide interactions by hybridisation to arrays: the influence of dangling ends on duplex yield.

Effects of dangling ends on duplex yield have been assessed by hybridisation of oligonucleotides to an array of oligonucleotides synthesised on the surface of a solid support. The array consists of decanucleotides and shorter sequences. One of the decanucleotides in the array was fully complementary to the decanucleotide used as solution target. Others were complementary over seven to nine bases, with overhangs of one to three bases. Duplexes involving different decanucleotides had different overhangs at the 3' and 5' ends. Some duplexes involving shorter oligonucleotides had the same regions of complementarity as these decanucleotides, but with fewer overhanging bases. This analysis allows simultaneous assessment of the effects of differing bases at both 5' and 3' ends of the oligonucleotide in duplexes formed under identical reaction conditions. The results indicate that a 5' overhang is more stabilising than a 3' overhang, which is consistent with previous results obtained with DNA overhangs. However, it is not clear whether this is due to the orientation of the overhang or to the effect of specific bases.     

Spatial relationships between the anterior centriole and the mitotic center during interphase in the amoebae of the myxomycete Physarum polycephalum

Amoebae of the Myxomycete Physarum polycephalum in the interphase state typically contain only one proflagellar apparatus in which the anterior kinetosome (anterior centriole) is attached to the microtubule organizing center 1 (mtoc 1). We built strains possessing more than one mtoc 1 and a variable number of anterior centrioles to allow the appearance of new structures. In 8% of the amoebae of these strains, the 1:1 attachment between the anterior centriole and the mtoc 1 is not always respected. In nine cases studied using tridimensional reconstructions from ultrastructural thin sections, the pattern of attachment was more complex. A mtoc 1 could be linked to several anterior centrioles, and/or reciprocally an anterior centriole could be linked to several mtoc 1. In one case, an anterior centriole was not linked to a mtoc 1 and in three cases, a single centriole exhibited anterior and posterior characteristics. These observations suggest that (1) each pair of centrioles constitutes a morphological and physiological entity that is distinct from the mitotic center (mtoc 1); (2) the attachment of the anterior centriole to the mtoc 1 occurs at the end of each mitosis; (3) there is an inductory process during the morphogenesis of the link between the anterior centriole and the mtoc 1; (4) the anterior characteristics of a centriole can be present in the absence of the link with the mtoc 1; (5) the anterior and posterior characteristics of a centriole are not exclusive of each other, ruling out the existence of a lineage corresponding to the anterior centriole and a lineage corresponding to the posterior centriole; and (6) the differences between anterior and posterior centrioles result from a maturation process.     

Kinetics of formation of ferrioxamine B

Stopped-flow kinetic studies of the formation of ferrioxamine B were performed. Formation of the complex follows the rate law

where K_a is the acid dissociation constant of the iron(III) aquo species in 0.1 M formate buffer. At 25°C k₁ = 3.94 × 10²M^?1 sec^?1, k₂K_a = 1.18 × 10^?1 sec^?1, k₃ = 3.6 × 10^?1 sec^?1. Activation parameters for k₁ are ΔH^≠ = 11.7 kcal mole^?1 and ΔS^≠ = ?8 cal K^?1 mole^?1. An associative mechanism is proposed. Attachment of the first chelate ring is the slow step and favorably positions the second chelate ring for attachment. Coordination of two chelate rings favorably positions the third chelate ring for attachment. These results are compared to kinetics of formation of model complexes and to a previous study of the formation of ferrioxamine B in which attachment of the third chelate ring was proposed as the slow step     

Banding patterns of the chromosomes ofCercopithecus neglectus: Comparison withMiopithecus talapoin andErythrocebus patas

The G, Q, and C bands and the location of the nucleolar organizing regions (NORs) of the chromosomes of two male Cercopithecus neglectusare described. The diploid number of the species is 2n =62. Comparison with the karyotypes of Miopithecus talapoin (2n =54), and Erythrocebus patas (2n =54)showed the presence of total banding homeology for only 10 chromosome pairs.