Mechanical modulation of pressure-volume characteristics of contracted canine airways in vitro

In normal humans and dogs, the airways do not constrict to closure even when maximally stimulated. However, airway closure can be produced in isolated canine lobes and bronchial segments that are stimulated with maximal concentrations of bronchoconstrictors. These observations suggest that under normal conditions, physiological mechanisms to limit bronchoconstriction exist in vivo. In this investigation, we evaluated how mechanical factors that influence airway smooth muscle contractility contribute to the modulation of the pressure-volume characteristics of contracted canine intraparenchymal airways in vitro. Our results demonstrated that maximal and even submaximal contractile stimuli can produce airway closure in bronchi that are allowed to contract under isobaric conditions. However, the effectiveness of bronchoconstrictors is significantly reduced when the airways are subjected to tidal volume oscillations during contraction. In addition, airways contracted isovolumetrically at low volumes exhibit a markedly reduced sensitivity to submaximal concentrations of acetylcholine. This may limit bronchoconstriction at low lung volumes and transpulmonary pressures where the effectiveness of parenchymal stress in keeping the airways open is reduced. Together these factors could provide a mechanism by which bronchoconstriction is limited to low levels of airway resistance under normal conditions in vivo.     

Genotypic interactions in an aphid-host plant relationship: Uroleucon rudbeckiae and Rudbeckia laciniata

Summary Four clones of the aphid Uroleucon rudbeckiae were grown on four clones of the host plant Rudbeckia laciniata. Age-specific fecundities were used to determine the fitness, F _i , of each individual aphid. The analysis of variance for F _i revealed that (1) plant genotype has a significant effect on aphid fitness; (2) there is an interaction between aphid and host plant genotypes with respect to aphid fitness; and (3) aphid fitness is affected by phenotypic differences among individual host plants. Result (2) supports the hypothesis that genotypic interactions between aphid and host may maintain genetic diversity in aphid populations. The results of a preference test, while not significant at customary probability levels, suggested that aphids will choose to feed on plants which confer greater fitness.     

Genetic characterization of spoilage pseudomonads isolated from retail-displayed beef

Aim:  This study genetically characterized Pseudomonas isolated from beef using the random amplification of polymorphic DNA (RAPD) method and correlate predominant genotypes with spoilage changes.
Methods and Results:  Pseudomonads were recovered from beef loins and steaks on days 0, 2, 4, 6, 8 and 10. A total of 309 pseudomonads were grouped into 50 RAPD types (>85% similarity). One major RAPD type contained 45% of the isolates comprising 71%, 45%, 31%, 35%, 50% and 37% of isolates from days 0, 2, 4, 6, 8 and 10, respectively, from steaks and 48% of the isolates recovered from beef loins. Nineteen RAPD types consisted of isolates that were shared between more than two sampling times, whereas the remaining 31 types were unique to one particular time.
Conclusions:  A genetically diverse Pseudomonas population was present on the loins and steaks at each sampling time. Although pseudomonads associated with beef loins were transferred to the steaks prepared from it, a genetically diverse Pseudomonas population emerged during the retail display.
Significance and Impact of the Study:  Information about the heterogeneous nature of Pseudomonas recovered from meat would help understanding the spoilage owing to predominant strains. The meat industry can use the knowledge to develop control strategies for prevalent spoilage strains.     

The use of traps in sampling mosquito populations

Mosquito populations in southern England were sampled by animal baited, carbon dioxide and light traps. Cylindrical traps baited with rabbits caught both zoophilous and ornithophilous species, but very few individuals were caught when they were baited with chickens. Direct bait catches, however, showed that ornithophilous species were not attracted to rabbits outside traps. Many more species were caught in Trinidad traps baited with dry ice than in cylindrical traps. A New Jersey light trap caught unfed females and males of a few species, many common species were not attracted to light.

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Zusammenfassung In Trinidad-Fallen, die mit Labor-Mäusen beködert auf der Insel Brownsea in Südengland aufgestellt waren, wurden nur sehr wenige Aedes detritus und Mansonia richiardii gefangen. Zylindrische, mit Kaninchen beköderte Metallfallen fingen erwachsene Anopheles plumbeus, Ae. cinereus, Ae. punctor, Ae. detritus, Culiseta annulata, C. torrentium, M. richiardii und auch C. morsitans und C. pipiens, obwohl sie hauptsächlich Vogelparasiten sind. Außerhalb der Fallen wurden Kaninchen von M. richiardii und Aedes-Arten gestochen aber nicht von ornithophilen Arten. In Fallen, die mit Hühnchen beködert waren, wurden nur sehr wenige C. morsitans und C. pipiens gefangen, und keine versuchten die Hühnchen außerhalb der Fallen zu stechen. Mit Trockeneis beköderte Trinidad- und Zylinder-Fallen fingen Ae. punctor, Ae. detritus, Ae. cantans, Ae. annulata, C. morsitans, C. pipiens und M. richiardii, dazu wurden in Trinidad-Fallen A. plumbeus, A. claviger und Ae. geniculatus gefangen. Sie fingen mehr als die zylindrischen Fallen.Eine New Jersey-Lichtfalle fing 12 Mückenarten, am häufigsten Ae. detritus. Nüchterne Weibchen herrschten vor, Männchen bildeten nur einen geringen Prozentsatz des Fanges.