Endogenous cyclic AMP in thyroid cell culture. Effect of thyroid-stimulating hormone and dibutyryl cyclic AMP

We have studied the variations of endogenous cyclic AMP levels in thyroid cells cultured over a period of 7 days in several conditions: in the presence of thyroid-stimulating hormone or dibutyryl cyclin AMP which both promote the aggregation of isolated cell into follicles, and in their absence when cells develop as a typical monolayer. In follicle-forming cells, the cyclic AMP level was found to rise during the first day of culture, then to fall rapidly. In monolayer-forming cells, the cyclic AMP content slightly increases attaining the same level as found in other cells at the fourth day, which remains stable till the seventh day. We have investigated the response of these cells to the acute effect of thyroid-stimulating hormone: only cells cultured in the presence of dibutyryl cyclic AMP retain the capability of increasing their cycli AMP concentration whereas monolayer-forming cells do not preserve this quality of thyroid cells.     

Die verschiedenen Typen im Korollenbau vonLithospermum

Ohne Zusammenfassung     

Accumulation of a Protein Required for Division During the Cell Cycle of Escherichia coli

A heat-labile protein required for division accumulates during the duplication cycle of Escherichia coli. Its formation appears to commence shortly after the cell divides, and it reaches a maximal amount shortly before the next division. A plausible mechanism for timing cell division depends on building up the critical amount of this protein. Completion of deoxyribonucleic acid (DNA) replication is also necessary for division to occur, but it does not uniquely initiate division. The evidence for these conclusions comes from heat-shock experiments; heating to 45 C for 15 min delays division increasingly with the age of a cell. A heat shock given near the end of a cycle delays division for about 30 min, whereas at the beginning of the cycle it hardly affects division. The net result is synchronization of cell division. The effect of heat is increased in bacteria which have incorporated p-fluoro-phenylalanine into their proteins. When the incorporation is early and the heat shock is late in the cycle, division is delayed by about 30 min, indicating that the division protein is synthesized early even though its sensitivity is not observed until later. At any time in the cell cycle, heat shock simply delays total protein and DNA synthesis ((3)H-thymidine uptake) for approximately 14 min. DNA replication and cell division are thus discoordinated, since DNA replication is not synchronized by the treatment.     

A cluster of Ankyrin and Ankyrin-TPR repeat genes is associated with panicle branching diversity in rice

The number of grains per panicle is an important yield-related trait in cereals which depends in part on panicle branching complexity. One component of this complexity is the number of secondary branches per panicle. Previously, a GWAS site associated with secondary branch and spikelet numbers per panicle in rice was identified. Here we combined gene capture, bi-parental genetic population analysis, expression profiling and transgenic approaches in order to investigate the functional significance of a cluster of 6 ANK and ANK-TPR genes within the QTL. Four of the ANK and ANK-TPR genes present a differential expression associated with panicle secondary branch number in contrasted accessions. These differential expression patterns correlate in the different alleles of these genes with specific deletions of potential cis-regulatory sequences in their promoters. Two of these genes were confirmed through functional analysis as playing a role in the control of panicle architecture. Our findings indicate that secondary branching diversity in the rice panicle is governed in part by differentially expressed genes within this cluster encoding ANK and ANK-TPR domain proteins that may act as positive or negative regulators of panicle meristem’s identity transition from indeterminate to determinate state.     

The Future of Tropical Forest Species1

Deforestation and habitat loss are widely expected to precipitate an extinction crisis among tropical forest species. Humans cause deforestation, and humans living in rural settings have the greatest impact on extant forest area in the tropics. Current human demographic trends, including slowing population growth and intense urbanization, give reason to hope that deforestation will slow, natural forest regeneration through secondary succession will accelerate, and the widely anticipated mass extinction of tropical forest species will be avoided. Here, we show that the proportion of potential forest cover remaining is closely correlated with human population density among countries, in both the tropics and the temperate zone. We use United Nations population projections and continent‐specific relationships between both total and rural population density and forest remaining today to project future tropical forest cover. Our projections suggest that deforestation rates will decrease as population growth slows, and that a much larger area will continue to be forested than previous studies suggest. Tropical forests retracted to smaller areas during repeated Pleistocene glacial events in Africa and more recently in selected areas that supported large prehistoric human populations. Despite many caveats, these projections and observations provide hope that many tropical forest species will be able to survive the current wave of deforestation and human population growth. A strategy to preserve tropical biodiversity might include policies to improve conditions in tropical urban settings to hasten urbanization and preemptive conservation efforts in countries with large areas of extant forest and large projected rates of future human population growth. We hope that this first attempt inspires others to produce better models of future tropical forest cover and associated policy recommendations.     

Responses of domestic chicks (Gallus gallus domesticus) to multimodal aposematic signals

Many aposematic prey combine their visual warning signals withadditional signals. Together, these signals constitute a multimodalor multicomponent warning display. The additional signals arethought to increase the effects of the visual signals on predators.Olfactory signals are much emphasized, but later studies haveshown that also auditory signals like the buzzing of certaininsects might have multimodal effects. The wasp displays typicalvisual aposematic signals, black and yellow stripes, but doesalso emit a characteristic buzzing. We wanted to test if, andin what way, the visual and acoustic display of the wasp hasan aversive function on the predators. We therefore conducteda 12-trial discrimination-learning task on inexperienced chicksto study whether there are innate biases toward these signalsand how they affect the speed of avoidance learning. We alsoperformed three extinction-learning trials to study how memorablethe signals were to the chicks. We show that the visual signalsin the display of the wasp contribute to the protection frompredators but in different ways; the yellow color had an aversiveeffect on inexperienced predators, while the striped patternimproved the aversion learning. The sound did not enhance theinnate aversions but increased the aversion learning of stripesin green prey.     

Process‐based long‐term evaluation of an ecological network of calcareous grasslands connected by sheep herding

This paper evaluates the long‐term effect of an ecological network of calcareous grasslands, a habitat type that experienced dramatic habitat loss and fragmentation during the 20th century, on species richness of habitat specialist plants. Calcareous grasslands are of special conservation concern as the habitat type with the highest diversity in plant and invertebrate species in central Europe. A baseline survey in 1989 established complete vascular plant species lists for all 62 previously abandoned calcareous grassland patches in the study area and assessed the presence of 48 habitat specialist plant species. An ecological network was initiated in 1989 to reconnect these patches with existing grazed pastures (core areas) through large flock sheep herding where feasible, as sheep are thought to be the primary dispersal vectors for calcareous grassland plants. An evaluation survey in 2009 showed significant increase in species richness of habitat specialist plants in patches reconnected by sheep herding, indicating successful colonizations by habitat specialist plants, while ungrazed patches showed no significant change. Observed increase in species richness between 1989 and 2009 was related to connectivity by sheep herding and the presence of a diversity of structural elements providing microsites for establishment. Baseline species richness of the patches, which had been abandoned since at least 1960, was associated with patch area, supporting the effect of ecological drift, and with vegetation type, which suggests that delays in extinction may be related to site factors governing the strength of competition with later seral species. The implementation of this ecological network represents a long‐term ‘natural experiment’ with baseline data, manipulation, and evaluation of hypothesized effects on a clearly defined target variable. It thus provides much needed empirical evidence that species loss in fragmented calcareous grassland communities can be counteracted by restoring functional connectivity among remnant patches.     

Seasonal Variation in Human Salivary Cortisol Concentration

Measurement of cortisol concentration can contribute important information about an individual's ability to adjust to various environmental demands of both physical and psychosocial origin. However, one uncertainty that affects the possibilities of correctly interpreting and designing field studies is the lack of observations of the impact of seasonal changes on cortisol excretion. For this reason, the month‐to‐month changes in diurnal cortisol concentration, the awakening cortisol response (ACR), maximum morning concentration, and fall during the day were studied in a group of 24 healthy men and women 32 to 61 yrs of age engaged in active work. On one workday for 12 consecutive months, participants collected saliva at four time points for determination of cortisol: at awakening, +30 min, +8 h, and at 21:00 h. Data were analyzed by a repeated measures design with month (12 levels) and time‐of‐day (4 levels) as categorical predictors. Cortisol concentrations were analyzed on a log scale. The diurnal pattern of cortisol was similar across months (interaction between month and time of day: p>0.4). The main effects of month and time‐of‐day were statistically significant (p <0.001). Highest concentrations were observed in February, March, and April, and lowest concentrations were observed in July and August. There were no statistically significant effects in any of the other measures, or between men and women. In conclusion, a seasonal variation in salivary cortisol concentrations was detected in an occupationally active population. Thus, seasonal variation needs to be taken into account when designing and evaluating field studies and interventions and when making comparisons across studies.     

Effects of alcohol mixed with energy drink and alcohol alone on subjective intoxication

Recent studies suggest that the combination of caffeine-containing drinks together with alcohol might reduce the subjective feelings of alcohol intoxication—the so-called “masking effect”. In this study, we aimed to review the effects of alcohol in combination with caffeine or energy drink with special focus on the “masking effect”. Fifty-two healthy male volunteers were analysed concerning breath alcohol concentration and subjective sensations of intoxication using a 18 item Visual Analogue Scale in a randomised, double-blinded, controlled, four treatments cross-over trial after consumption of (A) placebo, (B) alcohol (vodka 37.5 % at a dose of 46.5 g ethanol), (C) alcohol in combination with caffeine at a dose of 80 mg (equivalent to one 250 ml can of energy drink) and (D) alcohol in combination with energy drink at a dose of 250 ml (one can). Primary variables were headache, weakness, salivation and motor coordination. Out of four primary variables, weakness and motor coordination showed a statistically significant difference between alcohol and non-alcohol group, out of 14 secondary variables, five more variables (dizziness, alterations in sight, alterations in walking, agitation and alterations in speech) also showed significant differences due mainly to contrasts with the non-alcohol group. In none of these end points, could a statistically significant effect be found for the additional ingestion of energy drink or caffeine on the subjective feelings of alcohol intoxication. This within-subjects study does not confirm the presence of a “masking effect” when combining caffeine or energy drink with alcohol.