Regeneration of plantlets from in vitro cultured cotyledons of white spruce (Picea glauca (Moench) Voss)

Adventitious shoot production from seedling cotyledons was investigated for white spruce [Picea glauca (Moench) Voss]. The age of the seedling was found to be important for shoot induction response, the optimum seedling age being 7 to 8 days old. Prior to that age, although response was seen, the multiplication rate was lower. After 7 to 8 days, the capacity to produce shoots declined considerably. The optimum cytokinin (BA) concentration for bud induction was 2 M BA. The response to specific BA concentrations was independent of seedling age. The shoot regeneration presented here was highly reproducible and provided primary multiplication rates of approximately 100 to 150 shoots per seedling which had an average of 6 cotyledons. Approximately 30% of 40 regenerated shoots were induced to differentiate roots and all the rooted plantlets were successfully transplanted to soil.Abbreviations BA Benzyladenine - IBA indole-3-butyric acid. NRCC No. 29142     

Transfilter studies on neural induction in the newt.

In order to study the transmission mechanism of neuralising signals during primary embryonic induction, the interacting components (competent newt gastrula ectoderm and dorsal lip tissues) were separated by filter membranes of varying pore size. Nuclepore filters with nominal pore size from 0.1 to 8 mum were employed and the neuralising effect was shown to traverse all of these membranes. Electron microscopic examination did not reveal any cytoplasmic processes in the pores and the authors conclude that the morphogenetic signals are carried by transmissable compounds rather than through direct cytoplasmic contacts.     

Space efficient system for whole-body exposure of unrestrained rats to 900 MHz electromagnetic fields

The aim of this study was to design, implement and analyze a space-efficient setup for the whole-body exposure of unrestrained Wistar rats to radiofrequency (RF) electromagnetic fields at 900 MHz. The setup was used for 2 years in a cocarcinogenesis study and part of it for 5 weeks in a central nervous system (CNS) study. Up to 216 rats could be placed in separate cages in nine different exposure chambers on three racks requiring only 9 m2 of floor area (24 rats per m2). Chambers were radial transmission lines (RTL), where the rats could freely move in their cages where food and drinking water was provided ad libitum except during RF exposure periods. Dosimetrical analysis was based on FDTD computations with heterogeneous rat models and was validated with calorimetrical measurements carried out with homogeneous phantoms. The estimated whole-body average specific absorption rates (SAR) of rats were 0 (sham), 0.4, and 1.3 W/kg in the cocarcinogenesis study and 0 (sham), 0.27, and 2.7 W/kg in the CNS study with an estimated uncertainty of 3 dB (K = 2). The instantaneous and lifetime variations of whole-body average SAR due to the movement of rats were estimated to be 2.3 and 1.3 dB (K = 1), respectively.     

Can AMP induce sputum eosinophils,even in subjects with complete asthma remission?

Background

The definition of "clinical asthma remission" is based on absence of symptoms and use of medication. However, in the majority of these subjects airway inflammation is still present when measured. In the present study we investigated whether "complete asthma remission", additionally defined by the absence of bronchial hyperresponsiveness (BHR) and the presence of a normal lung function, is associated with the absence of airway inflammation.

Methods

Patients with a former diagnosis of asthma and a positive histamine provocation test were re-examined to identify subjects with complete asthma remission (no asthma symptoms or medication, PC₂₀ histamine > 32 mg/ml, FEV₁ > 90% predicted). Patients with PC₂₀ histamine ≤ 32 mg/ml were defined as current asthmatics and were divided in two groups, i.e. asthmatics with and without BHR to adenosine 5''monophoshate (AMP). Sputum induction was performed 1 week before and 1 hour after AMP provocation. Sputum induction and AMP provocation were previously shown to be sensitive markers of airway inflammation.

Results

Seven patients met criteria for complete asthma remission. Twenty-three were current asthmatics, including twelve without hyperresponsiveness to AMP. Subjects with complete asthma remission showed no AMP-induced sputum eosinophilia (median (range) 0.2 (0 - 4.6)% at baseline and 0.2 (0 - 2.6)% after AMP). After AMP, current asthmatics had a significant increase in sputum eosinophils (0.5 (0 - 26.0)% at baseline and 2.6 (0 - 32.0) % after AMP), as had the subgroup of current asthmatics without hyperresponsiveness to AMP (0.2 (0 - 1.8)% at baseline and 1.3 (0 - 6.3)% after AMP).

Conclusions

Subjects with complete asthma remission, in contrast to subjects with current asthma, do not respond with eosinophilic inflammation in sputum after AMP provocations. These data lend support to the usefulness of the definition of complete asthma remission.     

Model-Based Analysis of Mechanisms Responsible for Sleep-Induced Carbon Dioxide Differences

This work describes a comprehensive mathematical model of the human respiratory control system which incorporates the central mechanisms for predicting sleep-induced changes in chemical regulation of ventilation. The model integrates four individual compartments for gas storage and exchange, namely alveolar air, pulmonary blood, tissue capillary blood, body tissues, and gas transport between them. An essential mechanism in the carbon dioxide transport is its dissociation into bicarbonate and acid, where a buffering mechanism through hemoglobin is used to prevent harmfully low pH levels. In the current model, we assume high oxygen levels and consider intracellular hydrogen ion concentration as the principal respiratory control variable. The resulting system of delayed differential equations is solved numerically. With an appropriate choice of key parameters, such as velocity of blood flow and gain of a non-linear controller function, the model provides steady-state results consistent with our experimental observations measured in subjects across sleep onset. Dynamic predictions from the model give new insights into the behaviour of the system in subjects with different buffering capacities and suggest novel hypotheses for future experimental and clinical studies.     

Genetic variability of fragmented stands of pedunculate oak (Quercus robur) in Finland

The genetic structure of 33 natural Quercus robur stands in Finland was studied using 13 allozyme loci to analyze the effects of fragmentation in a wind-pollinated tree species. The present fragmented and discontinuous distribution of oak is a result of both short-term human impact and long-term climatic and geological change, including post-glacial land uplift. In accordance with general expectations, genetic diversity in small populations was lower than that in large populations, and differentiation among small populations was higher than that among large populations. Heterozygote deficiency was more pronounced in large populations, which is proposed to be a Wahlund effect created by either spatial sub-structuring or the existence of synchronized flowering lineages. Also genetic differentiation was higher and diversity lower in Finland than the estimates reported for Central Europe. There were differences in the genetic structure on sites of different geological age. We suggest that on most geologically old sites drift has a prominent effect whereas on younger sites also founder effects may be important.     

Evidence of an antilisterial factor induced by wounding of iceberg lettuce tissues

AIMS: To examine the influence of wound-associated reactions in cut iceberg lettuce (Lactuca sativa L.) tissues on the fate of Listeria monocytogenes. METHODS AND RESULTS: Aqueous extracts prepared from shredded iceberg lettuce before and after storage in high oxygen permeability film were inoculated with L. monocytogenes. Listeria monocytogenes grew in extracts prepared from fresh lettuce. In contrast, inhibition ranging from arrested growth to a decline in cell viability was observed in extracts prepared from samples stored for 1-3 days. Similar behaviour was evident in lettuce shreds inoculated with 10(5) CFU g(-1)L. monocytogenes immediately after processing or after 3 days in storage. Heat treatment of the cut tissues at 47 degrees C for 3 min before storage diminished the inhibitory effect. CONCLUSIONS: The results provided evidence that an antilisterial factor or factors are released by wounded iceberg lettuce tissues. Antilisterial activity was mitigated by heat treatment of the lettuce. SIGNIFICANCE AND IMPACT OF STUDY: This study indicates that intrinsic factors associated with plant metabolism could play a significant role in the ecology of human pathogens in packaged horticultural products.