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61.
Some behavioral and physical defenses of Lymantria dispar (L.) pupae are described. It was found that the layer of webbing surrounding pupae significantly reduced oviposition rates in the pupal parasitoid Brachymeria intermedia (Nees) (Hymenoptera, Chalcididae). The reasons for this reduction and consequent parasitoid responses were investigated. The role of these behaviors in this host parasitoid relationship are discussed.
Résumé Le comportement défensif des chrysalides de Lymantria dispar L. consiste en cambrage et en tournoiement. Les chrysalides encoconées étaient plus sensibles aux stimuli tactiles que celles qui ont été extraites des cocons. Brachymeria intermedia Nees avait moint de succès dans l'insertion complète de la tarière dans des chrysalides encoconées qu'extraites, car elles devenaient empêtrées dans le cocon quand la chrysalide se défendait. Il y avait différentes réponses du parasitoïde à l'empêtrement. Elles comprenaient l'abandon de l'attaque par un départ, la remise en selle sur l'hôte, la morsure à travers les fils du cocon, l'attaque d'un hôte voisin, le repos ou la toilette. Les taux d'insertion de la tarière pouvaient être augmentés par l'élimination artificielle de quelques fils. La durée des opérations était plus courte sur les chrysalides plus petites. La discussion a porté sur l'importance de ces comportements sur les relations de ces parasitoïdes avec leurs hôtes.相似文献
62.
The blue light dependent utilization of nitrate by green algae under common air and high irradiances, besides its assimilatory nature, is associated with the release of NO2
– and NH4
+ to the culture medium. If the CO2 content of the sparging air was increased up to 2%, previously excreted NO2
– and NH4
+ were rapidly assimilated. When under air and high irradiances the cell density in the culture reached values corresponding to 25 g Ch 1.ml-1, no further growth was observed and the highest values of NO3
– consumption and NO2
– and NH4
+ release were attained. Besides low CO2 tensions, increasing NO3
– concentrations in the medium stimulated the release of NO3
– and NH4
+. Under CO2-free air the consumption of NO3
– and the release of NO2
– and NH4
+ on a total N bases were almost stoichiometric and their rates saturated at much lower irradiances than under air. Under CO2-free air high rates of NO2
– release were only observed under the blue radiations that were effectively absorbed by photosynthetically active pigments, i.e. 460 nm, but not under 404 and 630 nm radiations. However, the simultaneous illumination of the cells with 404 and 630 nm monochromatic light showed a remarkable synergistic effect on NO2
– release.The results are discussed in terms of the close relationship between C and N metabolism, the photosynthetic reducing power required to convert NO
inf3
sup±
-N into R – NH2-N and the blue light activation of nitrate reductase. 相似文献
63.
64.
Summary The metabolic cost of active sodium transport was determined in toad bladder at different gradients of transepithelial potential, , by continuous and simultaneous measurements of CO2 production and of transepithelial electric current. Amiloride was used to block active sodium transport in order to assess the nontransport-linked, basal, production of CO2 and the passive permeability of the tissue. From these determinations active sodium transport,J
Na, and suprabasal CO2 production,
, were calculated. Since large transients inJ
Na and
frequently accompanied any abrupt change in , steady state conditions were carefully defined.Some 20 to 40 min were required after a change in before steady state of transport activity and of CO2 production were achieved. The metabolic cost of sodium transport proved to be the same whether the bladder expended energy moving sodium against a transepithelial electrical potential grandient of +50 mV or whether sodium was being pulled through the active transport pathway by an electrical gradient of –50 mV. In both cases the value of the ratio
averaged some 20 sodium ions transported per molecule of CO2 produced.When the Na pump was blocked by 10–2
m ouabain, the perturbations of the transepithelial electrical potential did not elicit changes ofJ
Na nor, consequently, of
.The independence of the ratio
from over the range ±50 mV indicates a high degree of coupling between active sodium transport and metabolism. 相似文献
65.
66.
Supernumerary chromosomes of two types have been observed in the grasshopper Eyprepocnemis plorans subsp. plorans. One of these (the B-type) is similar in size to an S autosome; the other is smaller (B-type). Both are telocentric and mitotically stable. The frequencies of individuals with the B-type supernumeraries in five natural populations were 56, 56, 70, 71 and 30 per cent respectively. The equivalent levels of the B-type supernumerary were 0, 0, 13, 3 and 0 per cent respectively. Because of the relative infrequency of the B-type only the B-type has been studied in detail. In males with 1B, anaphase I segregation of X and B was random in four populations but non-random in that from Otivar. Here the B was distinctive in having a secondary constriction near the centromere. A study of chiasma frequency among A-chromosomes revealed that the B-type supernumerary increases significantly both the mean chiasma frequency and the between-cell variance. A comparison of body morphometrics failed to reveal any effect of these B-chromosomes on the exophenotype. 相似文献
67.
Cytogenetic aspects of the cryptobranchid salamander Andrias davidianus of western China have been studied, including chromosome number and morphology, C-band patterns, meiosis, and the chromosomal localization of ribosomal 5S RNA genes. Our data regarding chromosome number (2n=60) and general chromosome morphology largely confirm the results of Morescalchi et al. (1977). The karyotype consists of 16 pairs of macrochromosomes that decrease gradually in relative length to 14 pairs of microchromosomes. Telocentric chromosomes are a conspicuous feature of the karyotype, representing more than half the genome. Differential staining reveals that all of the chromosomes, except four pairs of microchromosomes, have C-band heterochromatin in their centromeric regions, the amount varying irrespective of chromosome size. Faint bands of interstitial and telomeric C-band heterochromatin are found in mitotic chromosomes but are not seen in meiotic preparations. In C-banded mitotic preparations from a female, one of the smallest macrochromosome pairs is heteromorphic in respect to C-band heterochromatin and centromere position. In situ hybridization of an iodinated 5S RNA probe to meiotic chromosome preparations reveals that this repeated gene is clustered near the telomeric region of chromosome 7, a medium size telocentric, a location corresponding to a band of heterochromatin. Studies of spermatocytes indicate that the process of meiosis in A. davidianus closely resembles that of more advanced salamanders, and that the microchromosomes are meiotically stable. The significance of microchromosomes and chromosome morphology in the reorganization of salamander genomes during evolution is discussed on the basis of cytogenetic data available for A. davidianus and various other primitive and advanced salamanders. 相似文献
68.
Sequence of the S-layer gene of Thermus thermophilus HB8 and functionality of its promoter in Escherichia coli. 下载免费PDF全文
The nucleotide sequence of the slpA gene, which is responsible for the synthesis of the S-layer protein of Thermus thermophilus HB8, is described. This gene is transcribed as a unit in which the coding region is preceded by a 127-base-long leader mRNA sequence. The promoter region is also recognized by the RNA polymerase of Escherichia coli because of the presence of homologous -35 and -10 boxes. Homologies with other promoters from Thermus spp. are also presented. 相似文献
69.
Effects of Feeding and Drinking on Acetylcholine Release in the Nucleus Accumbens, Striatum, and Hippocampus of Freely Behaving Rats 总被引:4,自引:0,他引:4
Gregory P. Mark Pedro Rada Emmanuel Pothos Bartley G. Hoebel 《Journal of neurochemistry》1992,58(6):2269-2274
Extracellular levels of acetylcholine (ACh) were measured in the nucleus accumbens (NAC), striatum (STR), and hippocampus (HIPP) using microdialysis in 30-min intervals before, during, and after free-feeding in 20-h food-deprived rats. The effects on ACh in the NAC and STR were also observed in response to water intake in 20-h water-deprived animals. Neostigmine was used in the perfusate to improve ACh recovery. Basal ACh was sensitive to tetrodotoxin and low calcium, and therefore largely neuronal in origin. Feeding caused a 38% increase in extracellular ACh in the NAC and no change in the STR or HIPP. Dopamine was also increased in the NAC (48%) and to a lesser extent in the STR (21%) following feeding. Drinking caused 18-20% increases in ACh release in both the NAC and STR. In a separate experiment, ACh release in the NAC was monitored in 10-min intervals during free-feeding; ACh increased in the interval immediately following maximal food intake. These results suggest a site-specific increase in ACh release following feeding that cannot be solely attributed to the activation associated with this behavior. 相似文献
70.
Summary Papain was able to catalyze the one-step synthesis of Gly-Gly-PheNH2, from N-unprotected amino acid derivatives. Maximum synthetic activity was obtained for a pH value of 6.5 and for a ]PheNH2]/[Gly-GlyOEt] ratio of 6. The presence of an organic cosolvent, such as ethylene glycol, influenced the synthetic activity. Synthetic yield was higher than 65% for a 12.5 M cosolvent concentration. 相似文献