A human neuroblastoma cell line with a stable ornithine decarboxylase in vivo and in vitro

A human neuroblastoma cell line (Paju) grew in 10 mM difluoromethyl-ornithine, which at this concentration normally stops the growth of all mammalian cells. Ornithine decarboxylase from Paju was resistant to inhibition in vitro by difluoromethylornithine, and required 10 microM of the compound for 50% inhibition, whereas ornithine decarboxylase from SH-SY5Y cells (another human neuroblastoma) and from rat liver needed only 0.5 microM difluoromethylornithine. Paju ornithine decarboxylase also exhibited a long half-life (over eight hours) in vivo. The half-life of immunoreactive protein was significantly longer than that of the activity. The long half-life of ornithine decarboxylase in Paju cells leads to its accumulation to a specific activity of 2000 nmol/mg of protein per 30 min during rapid growth (the corresponding activity in SH-SY5Y cells was about 2.5). When partially purified ornithine decarboxylase from Paju cells was incubated with rat liver microsomes it was inactivated with a half-life of 75 min. This inactivation was accompanied by a fall in the amount of immunoreactive protein. In the same inactivating system partially purified SH-SY5Y ornithine decarboxylase had a half-life of 38 min and its half-life in vivo was 50 min. The corresponding values for rat liver ornithine decarboxylase were 45 min and 40 min, respectively. Rat liver microsomes also inactivated rat liver adenosylmethionine decarboxylase. These results suggest that Paju ornithine decarboxylase has an altered molecular conformation, rendering it resistant to (i) difluoromethylornithine and (ii) proteolytic degradation both in vivo and in vitro.     

Risk factors and 25 year risk of coronary heart disease in a male population with a high incidence of the disease: the Finnish cohorts of the seven countries study.

OBJECTIVE--To assess the efficacy of high serum cholesterol concentration, raised blood pressure, and smoking as predictors of coronary heart disease. DESIGN--Prospective cohort study of middle aged men conducted over 25 years. SETTING--Finish components of an ongoing international study (seven countries study). PARTICIPANTS--1520 Men who at age 40-59 in 1959 were free of clinically evident heart disease. INTERVENTIONS--At each follow up visit a detailed medical examination including resting electrocardiography was performed, blood pressure and serum total cholesterol concentration were measured, and smoking was assessed. MEASUREMENTS AND MAIN RESULTS--825 Deaths (54% of participants) occurred during follow up, of which 335 were due to coronary heart disease. The hazard ratio for death from coronary heart disease with respect to risk factors at entry were: for serum cholesterol concentrations above 8.4 mmol/l v below 5.2 mmol/l, 2.68 (95% confidence interval 1.62 to 4.42); for systolic blood pressure in the highest quintile v that in the lowest quintile, 2.46 (1.72 to 3.50); and for smoking 10 or more cigarettes daily v never smoking, 1.95 (1.36 to 2.79). The hazard ratios with respect to cholesterol concentrations and blood pressure remained constant during follow up but the ratio with respect to smoking diminished, mainly owing to men giving up the habit. The estimated conditional probability of a 50 year old man dying of coronary heart disease in the next 25 years ranged from 12% among those with the most favourable risk factor profile to 75% among those with the least favourable profile. CONCLUSIONS--High risk factor levels (as determined in this study) in middle aged men may greatly increase the absolute probability of death from coronary heart disease when the period of study is relevant to the human life span.     

Chloroplast DNA variation inAnemone s. lato (Ranunculaceae)

Chloroplast DNA of seven species belonging toAnemone (sectt.Omalocarpus, Anemonidium, andAnemonanthea),Hepatica, andPulsatilla have been analyzed by restriction enzymes. According to the dendrogram constructed, the sections ofAnemone and the generaHepatica andPulsatilla seem to be evolutionary approximately equidistant to each others. This supports the concept that these groups should be treated on a similar taxonomic level, either as genera or subgenera.     

Modelling crop growth and biomass partitioning to shoots and roots in relation to nitrogen and water availability,using a maximization principle

Many crop models relate the allocation of dry matter between shoots and roots exclusively to the crop development stage. Such models may not take into account the effects of changes in environment on allocation, unless the allocation parameters are altered. In this paper a crop model with a dynamic allocation parameter for dry matter between shoots and roots is described. The basis of the model is that a plant allocates dry matter such that its growth is maximized. Consequently, the demand and supply of carbon, nitrogen, and water is maintained in balance. This model supports the hypothesis that a functional equilibrium exists between shoots and roots.This paper explains the mathematical computation procedure of the crop model. Moreover, an analysis was made of the ability of a crop model to simulate plant dry matter production and allocation of dry matter between plant organs. The model was tested using data from a greenhouse experiment in which spring wheat (Triticum aestivum L.) was grown under different soil moisture and nitrogen (N) levels.Generally, the model simulations agreed well with data recorded for total plant dry matter. For validation data the coefficient of determination (r²) between simulated and measured shoot dry weight was 0.96. For the validation treatments r² was slightly lower, 0.94. In addition to dry matter production the model succeeded satisfactorily in simulating the dry weight of different plant organs. The response of simulated root to shoot ratio to the level of soil moisture was mainly in accordance with the measured data. In contrast, the simulated ratio seemed to be insensitive to the changes in the levels soil N concentration used in the experiment.The data used in the present study were not extensive, and more data are needed to validate the model. However, the results showed that the model responses to the changes in soil N and water level were realistic and mostly agreed with the data. Thus, we suggest that the model and the method employed to allocate dry matter between roots and shoots are useful when modelling the growth of crops under N and water limited conditions.     

Ribosomal RNA genes in Scots pine (Pinus sylvestris L.): Chromosomal organization and structure

The nuclear 18S, 5.8S and 25S rRNA genes exist as thousands of rDNA repeats in the Scots pine genome. The number and location of rDNA loci (nucleolus organizers, NORs) were studied by cytological methods, and a restriction map from the coding region of the Scots pine rDNA repeat was constructed using digoxigenin-labeled flax rDNA as a probe. Based on the maximum number of nucleoli and chromosomal secondary constrictions, Scots pine has at least eight NORs in its haploid genome. The size of the Scots pine rDNA repeat unit is approximately 27 kb, two- or threefold larger than the typical angiosperm rDNA unit, but similar in size to other characterized conifer rDNA repeats. The intergenic spacer region (IGS) of the rDNA repeat unit in Scots pine is longer than 20 kb, and the transcribed spacer regions surrounding the 5.8S gene (ITS1 and ITS2) span a region of 2.9 kb. Restriction analysis revealed that although the coding regions of rDNA repeats are homogeneous, heterogeneity exists in the intergenic spacer region between individuals, as well as among the rDNA repeats within individuals.     

Pyrophosphate-Fueled Na+ and H+ Transport in Prokaryotes

SUMMARY

In its early history, life appeared to depend on pyrophosphate rather than ATP as the source of energy. Ancient membrane pyrophosphatases that couple pyrophosphate hydrolysis to active H⁺ transport across biological membranes (H⁺-pyrophosphatases) have long been known in prokaryotes, plants, and protists. Recent studies have identified two evolutionarily related and widespread prokaryotic relics that can pump Na⁺ (Na⁺-pyrophosphatase) or both Na⁺ and H⁺ (Na⁺,H⁺-pyrophosphatase). Both these transporters require Na⁺ for pyrophosphate hydrolysis and are further activated by K⁺. The determination of the three-dimensional structures of H⁺- and Na⁺-pyrophosphatases has been another recent breakthrough in the studies of these cation pumps. Structural and functional studies have highlighted the major determinants of the cation specificities of membrane pyrophosphatases and their potential use in constructing transgenic stress-resistant organisms.     

Heat waves trigger swift changes in the diet and life-history of a freshwater snail

Hydrobiologia - Extreme climatic events, such as heat waves, may induce changes in nutrient acquisition by omnivorous ectotherms. Likely modulated by the intensity, frequency and duration of these...     

Larval life history and anti-predator strategies are affected by breeding phenology in an amphibian

Seasonal time constraints can pose strong selection on life histories. Time-constrained animals should prioritise fast development over predation risk to avoid unfavourable growing conditions. However, changes in phenology could alter the balance between anti-predator and developmental needs. We studied variation of anti-predator strategies in common frog (Rana temporaria) tadpoles in four populations from the two extremes of a latitudinal gradient across Sweden. We examined, under common conditions in the laboratory, the anti-predator responses and life histories of tadpoles raised with predatory Aeshna dragonfly larvae in two consecutive years with a difference of 20 days in breeding time in the north, but no difference in breeding time in the nouth. In a year with late breeding, northern tadpoles did not modify their behaviour and morphology in the presence of predators, and metamorphosed faster and smaller than tadpoles born in a year with early breeding. In the year with early breeding, northern tadpoles showed a completely different anti-predator strategy by reducing activity and developing morphological defences in the presence of predators. We discuss the possible mechanisms that could activate these responses (likely a form of environmentally-mediated parental effect). To our knowledge, this is the first study to show that a vertebrate modifies the anti-predator strategy of its offspring in response to natural variation in reproductive phenology, which highlights the need to consider phenology in studies of life-history evolution.