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911.
R. Socha J. Šula 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(6):382-387
Three different cultures of dimorphic bug,Pyrrhocoris apterus, were analyzed concerning diapause and its relation to wing morph pattern. The proportion of macropterous bugs was considerably
higher (36%) in the Mediterranean culture from Israel than that (1.3%) in the temperate culture from the Czech Republic. The
macropterous morph- and brachypterous morphrelated types of reproduction arrest, differing by the length of pre-oviposition
period, were distinguished in cultures analyzed. The reproduction arrest with an average pre-oviposition period of 38.2 days
in Mediterranean macropters and 18.5 days in macropters from selected macropterous strain, was found to be typical for macropterous
morph. Two different photoperiodic conditions induced macropterous morph-related reproduction arrest, the long-day (18 h light-6
h dark) photoperiod in macropterous strain macropters and the short-day (12 h light-12 h dark) photoperiod in Mediterranean
macropters. The brachypterous morph-related reproduction arrest, characterized by pre-oviposition period longer than 90 days,
occurred predominantly in diapausing brachypterous bugs. While the hibernal diapause of brachypterous bugs was characterized
by a very high level of the 78- and 82-kDa proteins in haemolymph, their content in haemolymph of macropters during macropterous
morph-related reproduction arrest was almost as low as in the reproductive adults. The variation of reproduction arrest in
relation to wing dimorphism represents an important feature in the life strategy ofP. apterus. 相似文献
912.
Tympanate hearing has evolved in at least 6 different orders of insects, but had not been reported until recently in the Diptera. This study presents a newly discovered tympanal hearing organ, in the parasitoid tachinid fly, Ormia ochracea. The hearing organ is described in terms of external and internal morphology, cellular organization of the sensory organ and preliminary neuroanatomy of the primary auditory afferents. The ear is located on the frontal face of the prothorax, directly behind the head capsule. Conspicuously visible are a pair of thin cuticular membranes specialized for audition, the prosternal tympanal membranes. Directly attached to these membranes, within the enlarged prosternal chamber, are a pair of auditory sensory organs, the bulbae acusticae. These sensory organs are unique among all auditory organs known so far because both are contained within an unpartitioned acoustic chamber. The prosternal chamber is connected to the outside by a pair of tracheae. The cellular anatomy of the fly's scolopophorous organ was investigated by light and electron microscopy. The bulba acustica is a typical chordotonal organ and it contains approximately 70 receptor cells. It is similar to other insect sensory organs associated with tympanal ears. The similarity of the cellular organization and tympanal morphology of the ormiine ear to the ears of other tympanate insects suggests that there are potent constraints in the design features of tympanal hearing organs, which must function to detect high frequency auditory signals over long distances. Each sensory organ is innervated by a branch of the frontal nerve of the fused thoracic ganglia. The primary auditory afferents project to each of the pro-, meso-, and metathoracic neuropils. The fly's hearing organ is sexually dimorphic, whereby the tympanal membranes are larger in females and the spiracles larger in males. The dimorphism presumably reflects differences in the acoustic behavior in the two sexes. 相似文献
913.
Low temperature field emission electron microscopy was used to determine the location of free water in soybean seeds. Frozen, hydrated soybean seeds were fractured, the water etched from the fractured surface, and then part of the etched surface was refractured. The resulting surface, which contained a freeze-fractured face as well as a freeze-etched face was coated with platinum and viewed on the cryostage of a low temperature field emission electron microscope. Two surfaces could be viewed simultaneously to determine the location of water in the seed tissue. Viewing the fractured surface gave an indication of the extent of hydration of the tissue. Viewing the etched surface detailed the macro- and microanatomy of the tissue. Viewing the intersection between the fractured and etched surfaces allowed observation of the environment of partially etched cells and organelles. The technique avoids artifacts associated with chemical fixation, dehydration, and critical-point drying, procedures that affect the water content of the seed. The technique does not affect the degree of hydration of the seed and can be used to localize water in the inter- and intracellular environment of the seed. This technique could find wide application in studies of water relationships of seeds during development, maturation, and imbibition. 相似文献
914.
Emanuel D. Rudolph 《American journal of botany》1996,83(5):661-671
The establishment of teaching laboratories for botany in the United States was strongly influenced in the early part of the 19th century by the founding of a laboratory of natural history at the Rensselaer School by Amos Eaton who inspired numerous educators, particularly women. By midcentury and later, botany programs were established at land-grant colleges and the so-called “new Botany” movement spread from them. In the latter part of the century additional changes were brought about by the influence of German laboratory activity and botanists’ reactions to the introduction of the Huxley-Martin biology programs to America. During these times, Americans were improving their own manufactured microscopes, laboratory supplies, and equipment capabilities. By the beginning of the 20th century, laboratory teaching of botanical subjects was widely accepted as normal in universities and colleges, as well as in some high schools. 相似文献
915.
We sampled 17 populations of a rare autotetraploid Aster kantoensis (Asteraceae) from three river systems located in central Japan, and studied them for allelic variation at 22 enzyme loci. There was no significant correlation between the actual population size and three genetic diversity parameters, suggesting that the effective population size was very small even for the large populations, i.e., even large populations may still have a high probability of being of recent origin and remain influenced by the founder effect. Compared to other autotetraploid species, the total genetic variation of A. kantoensis is small. The number of alleles and gene diversity of a population were not significantly different among the river systems, although the percentage of polymorphic loci was different. Genetic differentiation among river systems was larger than between populations within the river systems, thereby indicating that gene flow between river systems is small, especially between the Kinu River system and Tama or Sagami River systems. 相似文献
916.
S. PELTONEN M. JALLI K. KAMMIOVIRTA R. KARJALAINEN 《The Annals of applied biology》1996,128(3):465-477
Random amplified polymorphic DNA (RAPD) was used to assess genetic variation among 48 isolates of Drechslera teres originating from different sites in Finland. RAPD profiles were generated with five arbitrary 10-mer primers and revealed polymorphisms suitable for screening differentiation in this fungal population. Using UPGMA clustering analysis, a similarity coefficient of approximately 63% was observed between all D. teres isolates studied. The variation was, however, distributed on a small scale as different genotypes were found from the same plant. The isolates could not be grouped according to geographic origin, aggressiveness, growth rate or morphological features, indicating that the primers used in this study were neutral markers for these characters. The primers were, however, able to differentiate between isolates of Helminthosporium species (D. teres, Drechslera graminea and Bipolaris sorokiniana). 相似文献
917.
An empirical projection method is described to predict the magnitudes and signs of two-bond 13C-13C spin-coupling constants (2JCC) in aldopyranosyl rings. The method has been applied primarily to the interpretation of 2JCCC values, although the behavior of 2JCOC has also been examined in light of the new approach, producing results which may prove useful in the conformational analysis of O-glycosidic linkages in oligosaccharides. High-level ab initio calculations of 2JCC values in model compounds were found to be in agreement with the predictions. 相似文献
918.
Inositol lipid signaling relies on an InsP3-induced Ca2+ release from intracellular stores and on extracellular Ca2+ entry, which takes place when the Ca2+ stores become depleted of Ca2+. This interplay between Ca2+ release and Ca2+ entry has been termed capacitative Ca2+ entry and the inward current calcium release activated current (CRAC) to indicate gating of Ca2+ entry by Ca2+-store depletion. The signaling pathway and the gating mechanism of capacitative Ca2+ entry, however, are largely unknown and the molecular participants in this process have not been identified. In this article
we review genetic, molecular, and functional studies of wild-type and mutantDrosophila photoreceptors, suggesting that thetransient receptor potential mutant (trp) is the first putative capacitative Ca2+ entry mutant. Furthermore, several lines of evidence suggest that thetrp gene product TRP is a candidate subunit of the plasma membrane channel that is activated by Ca2+ store depletion. 相似文献
919.
Engineering challenges in high density cell culture systems 总被引:2,自引:0,他引:2
Ozturk SS 《Cytotechnology》1996,22(1-3):3-16
High density cell culture systems offer the advantage of production of bio-pharmaceuticals in compact bioreactors with high volumetric production rates; however, these systems are difficult to design and operate. First of all, the cells have to be retained in the bioreactor by physical means during perfusion. The design of the cell retention is the key to performance of high density cell culture systems. Oxygenation and media design are also important for maximizing the cell number. In high density perfusion reactors, variable cell density, and hence the metabolic demand, require constant adjustment of perfusion rates. The use of cell specific perfusion rate (CSPR) control provides a constant environment to the cells resulting in consistent production. On-line measurement of cell density and metabolic activities can be used for the estimation of cell densities and the control of CSPR. Issues related to mass transfer and mixing become more important at high cell densities. Due to the difference in mass transfer coefficients for oxygen and CO2, a significant accumulation of dissolved CO2 is experienced with silicone tubing aeration. Also, mixing is observed to decrease at high densities. Base addition, if not properly done, could result in localized cell lysis and poor culture performance. Non-uniform mixing in reactors promotes the heterogeneity of the culture. Cell aggregation results in segregation of the cells within different mixing zones. This paper discusses these issues and makes recommendations for further development of high density cell culture bioreactors. 相似文献
920.
Ülo Niinemets 《Ecological Research》1996,11(3):269-281
Dependencies of foliage arrangement and structure on relative irradiance and total height (TH) were studied in saplings ofAcer platanoides andQuercus robur. The distribution of relative foliar area and dry weight (leaf area and weight in a crown layer per total tree leaf area
and weight, respectively) were examined with respect to relative height (RH, height in the crown per TH) and characterized
by the Weibull function. The distributions of relative area and weight were nearly identical, and the differences between
them were attributable to a systematic decline in leaf dry weight per area with increasing crown depth. Foliage distribution
was similarly altered by tree size in both species; RH at foliage maximum was lower and relative canopy size (RCS, length
of live crown per TH) greater in taller trees. However, the distribution was more uniform inA. platanoides than inQ. robur. Apart from the size effects, relative irradiance also influenced canopy structure; RCS increased inQ. platanoides and decreased inQ. robur with increasing irradiance. As crown architecture was modified by irradiance, foliage distribution was shifted upwards with
decreasing irradiance inA. platanoides, but it was independent of irradiance inQ. robur. Higher foliage maximum at lower irradiance in more shade-tolerantA. platanoides is likely to contribute towards more efficient foliar display for light interception and increase the competitive ability
of this species in light-limited environments. Consequently, these differences in crown architecture and foliage distribution
may partly explain the superior behavior ofA. platanoides in understory. 相似文献