Heart Ratios at Different Stages in the Life Cycle of Lampreys

Heart ratios (heart weight/body weight. ×100) have been obtained for freshly killed and preserved (10% formalin) specimens of the lampreys Petromyzon marinus, Lampetra fluviatilis and L. planeri. Values for comparable stages were significantly higher in the preserved material, probably as a result of retention and fixation of blood in the heart chambers. The regression slope for the logarithmic relationship between heart and body weights was close to one in all stages of the three species investigated. A marked increase was observed in the heart ratio during metamorphosis, apparently attributable to an increase in the number and density of myocardial fibres. Heart ratios in the lamprey were generally higher than for most other fishes, with values of 0.1 and 0.3 being obtained for example in the case of freshly killed ammocoete and sexually mature adult stages of L. fluviatilis.     

An Experimental Test of Resistance to Cheatgrass Invasion: Limiting Resources at Different Life Stages

Variable densities of an invasive species may represent variation in invasion resistance, due to variation in resource availability. This study determined whether low- and high-density cheatgrass (Bromus tectorum L.) patches within a shadscale-bunchgrass community of western Utah, USA, can be explained by variation in resource availability. It also explored the possible role of seed limitation and enemy pressure on invasion patterns. Two parallel field experiments were conducted:(1) increasing resources within low-density cheatgrass patches and, conversely (2) reducing resources within high-density cheatgrass patches. Treatments were applied at three life stages separately and across all stages. In low-density cheatgrass patches (assumed to represent high resistance), a disturbance that reduced soil compaction had the strongest positive effect, significantly increasing biomass by 250% and density by 104% in comparison to the control. The second strongest effect was reducing neighbors (native grasses), which significantly increased cheatgrass biomass and density. These results indicate that resources are present in low-density cheatgrass patches, but they are unavailable without disturbance and/or are exploited by competitors, and hence represent resistance to invasion. In high-density cheatgrass patches (assumed to represent low resistance), nitrogen availability was important in maintaining cheatgrass densities. Reducing nitrogen (via sucrose addition) significantly decreased density (by 37%) but not biomass. Life stages of cheatgrass were differentially affected by these resource manipulations. In addition, herbivore (primarily grasshoppers) and pathogen (head smut) pressures were documented to affect cheatgrass density, but did not explain resistance patterns. Instead, we found that differential resource availability explains the observed variation in cheatgrass density, and variation in natural resistance.     

Aging of Soybean Seeds in Relation to Metabolism at Different Relative Humidities

The present study was carried out to clarify the relationshipsbetween respiration, moisture content and the aging of dry soybean(Glycine max) seeds under different storage conditions. Ethanolicfermentation increased with increasing relative humidity (RH)during storage. However, at 75% RH which corresponded to a watercontent of 15.2% in seeds, the production of ethanol ceasedafter one month of storage. The ethanol that had accumulatedwithin the container was re-absorbed by the seeds themselvesand disappeared entirely within 3 months, unless the seeds wereexposed to HCN gas. Similar changes were also found for methanol.The activity of mitochondria increased only in seeds storedat 75% RH, it reached a maximum after the third month of storageand then rapidly declined. The amounts of both CoA and acetylCoA in seeds that had been stored for 4 months were far lowerat 75% RH than at 53% RH, and the viability of soybean seedsstarted to decrease after the fourth month at 75% RH. Therefore,a major cause of the rapid deterioration of seeds at 75% RHat room temperature seems to be the rapid development of mitochondrialrespiration, which is accompanied by the consumption of CoAand its acetyl derivatives. By contrast, the slow deteriorationof seeds during long-term storage at 33% to 68% RH and/or atsubzero temperatures seems to be due to the toxic action ofacetaldehyde, an intermediate in ethanolic fermentation, whichcan slowly occur. (Received April 10, 1995; Accepted July 10, 1995)     

Survival of Salmonellae on and in Tomato Plants from the Time of Inoculation at Flowering and Early Stages of Fruit Development through Fruit Ripening

The fate of salmonellae applied to tomato plants was investigated. Five Salmonella serotypes were used to inoculate tomato plants before and after fruits set, either by injecting stems with inoculum or brushing flowers with it. Ripe tomato fruits were subjected to microbiological analysis. Peptone wash water, homogenates of stem scar tissues, and homogenates of fruit pulp were serially diluted and plated on bismuth sulfite agar before and after enrichment. Presumptive Salmonella colonies were confirmed by serological tests, PCR assay using HILA2 primers, and enterobacterial repetitive intergenic consensus PCR. Of 30 tomatoes harvested from inoculated plants, 11 (37%) were positive for Salmonella. Of the Salmonella-positive tomatoes, 43 and 40%, respectively, were from plants receiving stem inoculation before and after flower set. Two of eight tomatoes produced from inoculated flowers contained Salmonella. Higher percentages of surface (82%) and stem scar tissue (73%) samples, compared to pulp of Salmonella-positive tomatoes (55%), harbored the pathogen. Of the five serotypes in the inoculum, Montevideo was the most persistent, being isolated from tomatoes 49 days after inoculation, and Poona was the most dominant, being present in 5 of 11 Salmonella-positive tomatoes. Results suggest that Salmonella cells survive in or on tomato fruits from the time of inoculation at flowering through fruit ripening. Tomato stems and flowers are possible sites at which Salmonella may attach and remain viable during fruit development, thus serving as routes or reservoirs for contaminating ripened fruit.     

Enhanced Accumulation of BiP in Transgenic Plants Confers Tolerance to Water Stress

The binding protein (BiP) is an important component of endoplasmic reticulum stress response of cells. Despite extensive studies in cultured cells, a protective function of BiP against stress has not yet been demonstrated in whole multicellular organisms. Here, we have obtained transgenic tobacco (Nicotiana tabacum L. cv Havana) plants constitutively expressing elevated levels of BiP or its antisense cDNA to analyze the protective role of this endoplasmic reticulum lumenal stress protein at the whole plant level. Elevated levels of BiP in transgenic sense lines conferred tolerance to the glycosylation inhibitor tunicamycin during germination and tolerance to water deficit during plant growth. Under progressive drought, the leaf BiP levels correlated with the maintenance of the shoot turgidity and water content. The protective effect of BiP overexpression against water stress was disrupted by expression of an antisense BiP cDNA construct. Although overexpression of BiP prevented cellular dehydration, the stomatal conductance and transpiration rate in droughted sense leaves were higher than in control and antisense leaves. The rate of photosynthesis under water deficit might have caused a degree of greater osmotic adjustment in sense leaves because it remained unaffected during water deprivation, which was in marked contrast with the severe drought-induced decrease in the CO(2) assimilation in control and antisense leaves. In antisense plants, the water stress stimulation of the antioxidative defenses was higher than in control plants, whereas in droughted sense leaves an induction of superoxide dismutase activity was not observed. These results suggest that overexpression of BiP in plants may prevent endogenous oxidative stress.     

Stress-Reactivity of Lungs according to Metabolic Function Parameters at Different Stages of Postnatal Ontogenesis

Analysis of parameters of metabolic function of lungs with respect to lipid metabolism was performed in rats under conditions of acute experimental emotional-nociceptive stress. Study of the stress-sensitivity of lungs in the comparative-age aspect has shown different extent of changes of several parameters of lipid metabolism in pulmonary tissue in animals of different age. The results of the study demonstrate areactivity and high stress-stability of lungs with respect to surface-active properties, free-radical processes, and lipase activity in early postnatal ontogenesis.     

Different Functional and Structural Properties of Lactate Dehydrogenase Isozymes at Different Stages of Danio rerioOntogenesis

We studied properties of lactate dehydrogenase isozymes expressed at different stages of Danio rerioontogenesis. H₄-LDH and a minor fraction H₃M₁are expressed during embryonic development. The muscle isozyme (₄) appears after the beginning of muscle contractions in the embryo. ₄and ₄isozymes isolated from the heart and skeletal muscle of the adult fish, respectively, show significant differences in terms of Michaelis constant (K _m) activation energy (AE), and inactivation temperature. H₄-LDH isozymes isolated from unfertilized eggs, the skeletal muscle of larvae, and the heart of the adult fish differ inK _mand activation energy, as well as in inactivation temperature. We propose that these differences may be associated with a ligand interacting with the H₄isozyme at different steps of ontogenesis.     

Methodological Approaches to Evaluate Teratogenic Risk Using Birth Defect Registries: Advantages and Disadvantages

Background

Different approaches have been used in case-control studies to estimate maternal exposure to medications and the risk of birth defects. However, the performance of these approaches and how they affect the odds ratio (OR) estimates have not been evaluated using birth-defect surveillance programmes. The aim of this study was to evaluate the scope and limitations of three case-control approaches to assess the teratogenic risk of birth defects in mothers exposed to antiepileptic medications, insulin, or acetaminophen.

Methodology/Principal Findings

We studied 110,814 non-malformed newborns and 58,514 live newborns with birth defects registered by the Latin American Collaborative Study of Congenital Anomalies (ECLAMC) between 1967 and 2008. Four controls were randomly selected for each case in the same hospital and period, and three different control groups were used: non-malformed newborns (HEALTHY), malformed newborns (SICK), and a subgroup of SICK, only-exposed cases (OECA). Associations were evaluated using OR and Pearson''s chi-square (P<0.01). There were no concordance correlations between the HEALTHY and OECA designs, and the average OR differences ranged from 3.0 to 11.5 for the three evaluated medicines. The overestimations observed for HEALTHY design were increased as higher OR values were given, with a high and statistically significant correlation between the difference and the mean. On the contrary, the concordance correlations obtained between the SICK and OECA designs were quite good, with no significant differences in the average risks.

Conclusions

The HEALTHY design estimates the true population OR, but shows a high rate of false-positive results presumably caused by differential misclassification bias. This bias decreases with the increase of the proportion of exposed controls. SICK and OECA odds ratios cannot be considered a direct estimate of the true population OR except under certain conditions. However, the SICK and OECA designs could provide practical information to generate hypotheses about potential teratogens.     

Effects of Wind Waves versus Ship Waves on Tidal Marsh Plants: A Flume Study on Different Life Stages of Scirpus maritimus

Recent research indicates that many ecosystems, including intertidal marshes, follow the alternative stable states theory. This theory implies that thresholds of environmental factors can mark a limit between two opposing stable ecosystem states, e.g. vegetated marshes and bare mudflats. While elevation relative to mean sea level is considered as the overall threshold condition for colonization of mudflats by vegetation, little is known about the individual driving mechanisms, in particular the impact of waves, and more specifically of wave period. We studied the impact of different wave regimes on plants in a full scale flume experiment. Seedlings and adult shoots of the pioneer Scirpus maritimus were subjected to two wave periods at two water levels. Drag forces acting on, and sediment scouring occurring around the plants were quantified, as these are the two main mechanisms determining plant establishment and survival. Depending on life stage, two distinct survival strategies emerge: seedlings present a stress avoidance strategy by being extremely flexible, thus limiting the drag forces and thereby the risk of breaking. Adult shoots present a stress tolerance strategy by having stiffer stems, which gives them a higher resistance to breaking. These strategies work well under natural, short period wind wave conditions. For long period waves, however, caused e.g. by ships, these survival strategies have a high chance to fail as the flexibility of seedlings and stiffness of adults lead to plant tissue failure and extreme drag forces respectively. This results in both cases in strongly bent plant stems, potentially limiting their survival.     

Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum)

Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27–33, 34–57, 58–85, 86–99, and 27–99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34–57 DAS) and enlargement (58–85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.     

Antibacterial Immune Competence of Honey Bees (Apis mellifera) Is Adapted to Different Life Stages and Environmental Risks

The development of all honey bee castes proceeds through three different life stages all of which encounter microbial infections to a various extent. We have examined the immune strength of honey bees across all developmental stages with emphasis on the temporal expression of cellular and humoral immune responses upon artificial challenge with viable Escherichia coli bacteria. We employed a broad array of methods to investigate defence strategies of infected individuals: (a) fate of bacteria in the haemocoel; (b) nodule formation and (c) induction of antimicrobial peptides (AMPs). Newly emerged adult worker bees and drones were able to activate efficiently all examined immune reactions. The number of viable bacteria circulating in the haemocoel of infected bees declined rapidly by more than two orders of magnitude within the first 4–6 h post-injection (p.i.), coinciding with the occurrence of melanised nodules. Antimicrobial activity, on the other hand, became detectable only after the initial bacterial clearance. These two temporal patterns of defence reactions very likely represent the constitutive cellular and the induced humoral immune response. A unique feature of honey bees is that a fraction of worker bees survives the winter season in a cluster mostly engaged in thermoregulation. We show here that the overall immune strength of winter bees matches that of young summer bees although nodulation reactions are not initiated at all. As expected, high doses of injected viable E.coli bacteria caused no mortality in larvae or adults of each age. However, drone and worker pupae succumbed to challenge with E.coli even at low doses, accompanied by a premature darkening of the pupal body. In contrast to larvae and adults, we observed no fast clearance of viable bacteria and no induction of AMPs but a rapid proliferation of E.coli bacteria in the haemocoel of bee pupae ultimately leading to their death.     

冬小麦不同生育期植株与土壤的硫素动态

Ｓ是植物生命活动必需元素之一 ,在植物细胞的结构和生理生化功能中都具有不可替代的作用。如在植物体中参于蛋白质合成、光合作用、呼吸作用、脂类合成、生物固氮、糖代谢等。由于植物可通过多种途径获取所需的Ｓ素 ,如土壤、灌水、降雨、大气中的ＳＯ2 以及施用含硫化肥、农药等。因此 ,在过去 ,作物缺Ｓ的现象没有明显的表现。然而 ,近2 0～ 30年来 ,随着低Ｓ或无Ｓ高浓度化肥 (尿素、磷铵等 )的广泛应用、作物产量的不断提高、复种指数增加以及环保部门对含Ｓ废气排放标准的严格监测、控制等 ,植物的Ｓ素来源受到了限制 ,植物缺Ｓ现象逐…     

Survival of Rhizobium phaseoli in Coal-Based Legume Inoculants Applied to Seeds

Eight coals used as carriers in legume inoculants promoted the survival of Rhizobium phaseoli on pinto bean seeds. Although peat was more protective, most coal-based inoculants provided >10⁴ viable rhizobia per seed after 4 weeks.