Presence of prostaglandins E2 and A2 in canine gastric secretions

The presence of prostaglandins (PGs) was determined in gastric juice obtained from 3 conscious dogs, provided with a chronic gastric fistula. Outputs of acid (mequiv min^?1) and PGs (pg min^?1) were measured in gastric secretions stimulated by pentagastrin (100 or 200 ng kg^?1min^?1). Prostaglandin activity was estimated, after extraction and thin layer chromatography, by radioimmuno-assay of the PGB formed by treatment with alkali. Tritiated PGs were added to gastric juice for the purpose of correcting for PGs recovery. Using this method, the minimum mass of PGB which could be satisfactorily distinguished from zero was 25 pg. Prostaglandins A₂ and E₂ were present in pentagastrin-activated gastric secretions and averaged (mean ± SE, n = 8) 200.7 ± 18.1 and 260.1 ± 18.0 pg min^?1 respectively. The identity of PGA₂ and PGE₂ was confirmed by gas liquid chromatography combined with mass spectrometry. The amount of PGE₂ converted to PGA₂ during extraction, separation and conversion procedures was estimated from the amount of [³H] PGA₂ found when only [³H] PGE₂ had been added to a sample of gastric juice and averaged 14.5% ± 2.0. Our preliminary results support the possibility that PGE₂ and PGA₂ may be of physiological importance in the regulation of canine gastric secretions.     

Climatic forcing and larval dispersal capabilities shape the replenishment of fishes and their habitat‐forming biota on a tropical coral reef

Fluctuations in marine populations often relate to the supply of recruits by oceanic currents. Variation in these currents is typically driven by large‐scale changes in climate, in particular ENSO (El Nino Southern Oscillation). The dependence on large‐scale climatic changes may, however, be modified by early life history traits of marine taxa. Based on eight years of annual surveys, along 150 km of coastline, we examined how ENSO influenced abundance of juvenile fish, coral spat, and canopy‐forming macroalgae. We then investigated what traits make populations of some fish families more reliant on the ENSO relationship than others. Abundance of juvenile fish and coral recruits was generally positively correlated with the Southern Oscillation Index (SOI), higher densities recorded during La Niña years, when the ENSO‐influenced Leeuwin Current is stronger and sea surface temperature higher. The relationship is typically positive and stronger among fish families with shorter pelagic larval durations and stronger swimming abilities. The relationship is also stronger at sites on the coral back reef, although the strongest of all relationships were among the lethrinids (r = .9), siganids (r = .9), and mullids (r = .8), which recruit to macroalgal meadows in the lagoon. ENSO effects on habitat seem to moderate SOI–juvenile abundance relationship. Macroalgal canopies are higher during La Niña years, providing more favorable habitat for juvenile fish and strengthening the SOI effect on juvenile abundance. Conversely, loss of coral following a La Niña‐related heat wave may have compromised postsettlement survival of coral dependent species, weakening the influence of SOI on their abundance. This assessment of ENSO effects on tropical fish and habitat‐forming biota and how it is mediated by functional ecology improves our ability to predict and manage changes in the replenishment of marine populations.     

Indole metabolism in the pineal organ of the pigeon with special reference to melatonin-synthesizing cells

By means of radioimmunoassay a clear-cut peak of melatonin concentration was found in the pineal organ of the pigeon at the middle of the scotophase (Coisin et al. 1982a). The aim of the present study was to identify the cell type responsible for the nocturnal indole metabolism, including melatonin synthesis, in the pineal of this avian species. After a short-term incubation or organ culture in the presence of [3H]-indolic precursors, [3H]-5-hydroxytryptophan or [3H]-5-hydroxytryptamine, the relative amounts of deaminated and acetylated products occurring in the pineal organ were measured by the use of thin layer chromatography and liquid-scintillation counting. It was possible to modify the relative amounts of deaminated and acetylated indoles by the application of some inhibitors of monoamine oxidase and cyclic nucleotide phosphodiesterase. Irrespective of the experimental conditions, high-resolution autoradiography combined with the above-mentioned radiochemical experiments showed that the cells of the receptor line (modified photoreceptor cells) are responsible for indole storage and metabolism, and very probably also for melatonin biosynthesis. The other cell types of the pineal parenchyma did not display significant labeling.     

A Financial Market Model Incorporating Herd Behaviour

Herd behaviour in financial markets is a recurring phenomenon that exacerbates asset price volatility, and is considered a possible contributor to market fragility. While numerous studies investigate herd behaviour in financial markets, it is often considered without reference to the pricing of financial instruments or other market dynamics. Here, a trader interaction model based upon informational cascades in the presence of information thresholds is used to construct a new model of asset price returns that allows for both quiescent and herd-like regimes. Agent interaction is modelled using a stochastic pulse-coupled network, parametrised by information thresholds and a network coupling probability. Agents may possess either one or two information thresholds that, in each case, determine the number of distinct states an agent may occupy before trading takes place. In the case where agents possess two thresholds (labelled as the finite state-space model, corresponding to agents’ accumulating information over a bounded state-space), and where coupling strength is maximal, an asymptotic expression for the cascade-size probability is derived and shown to follow a power law when a critical value of network coupling probability is attained. For a range of model parameters, a mixture of negative binomial distributions is used to approximate the cascade-size distribution. This approximation is subsequently used to express the volatility of model price returns in terms of the model parameter which controls the network coupling probability. In the case where agents possess a single pulse-coupling threshold (labelled as the semi-infinite state-space model corresponding to agents’ accumulating information over an unbounded state-space), numerical evidence is presented that demonstrates volatility clustering and long-memory patterns in the volatility of asset returns. Finally, output from the model is compared to both the distribution of historical stock returns and the market price of an equity index option.     

Stability and degradation of mRNA

Differential mRNA stability plays an important role in the regulation of gene expression. Several recent advances have helped to define the general pathways by which mRNA is degraded in prokaryotic cells, although many details remain to be elucidated. Much less is known about the pathways of degradation in eukaryotic cells, but recent studies on specific systems have highlighted both differences from and similarities to prokaryotic pathways.     

Hyperthermic treatment of chromomycosis with disposable chemical pocket warmers

A case of chromomycosis in which hyperthermia proved effective is reported. The patient was a 56-year-old male bean curd maker who, without any previous history of minor trauma, developed on the extensor side of the left upper arm an eczematous lesion that underwent gradual radial expansion. The lesion showed a well-defined, 7×10 cm infiltrated erythematous plaque with the central area healed and, at the upper and lower borders, adherent scales and crusts on the surface. Histological examination revealed granulomatous changes in the dermis, as well as sclerotic cells within giant cells and microabscesses. On culturing,Fonsecaea pedrosoi was isolated. The patient was treated with disposable chemical pocket warmers, which were secured over the lesion with a rather tight elastic bandage, so that they kept the affected area warm for 24 hours a day. After a month of such hyperthermic treatment, the erythema and infiltration had decreased considerably, and microscopic examination and culture of the crusts both yielded negative results. Examination of biopsy specimens of the lesion after the third month showed that it had cicatrized. The treatment was stopped after 4 months, and no relapse occurred. We also summarize the published results of local hyperthermic treatment of chromomycosis in Japan.