A serotonergic system in the brain of the Antarctic fish, Trematomus bernacchii

The immunohistochemical distribution of serotonin-containing nerve fibres and cells has been described in the brain of the Antarctic fish, Trematomus bernacchii. The largest serotonergic system was associated with the diencephalic and rhombencephalic ventricles. In particular, serotonin-positive cells have been found in the lateral recess and neuropile zone of the diencephalic ventricle, where we have identified the serotonergic portion of the paraventricular organ. Numerous serotonin cells were localized in the dorsal nucleus of the raphe, the dorsal tegmental nucleus and the central gray. Two large cell groups, arranged in a pair of well-defined columns and connecting the central gray with the dorsal reticular formation, were immunostained in the region of the trigeminal nuclei. In addition, few positive cells have been found in the preoptic area and the cerebellar valvula, and few serotonergic nerve fibres, probably belonging to the lateral lemniscus, have been identified. The distribution of serotonin elements in the brain of T. bernacchii has been compared with that described in other fish, where it showed some modifications in the immunoreactive pattern. Finally, the lack of a serotonergic system at the level of the reticular superior formation has been reported; however, it was not possible to rule out a phylogenetic or environmental explanation.     

Oxygen: a master regulator of pancreatic development?

Beyond its role as an electron acceptor in aerobic respiration, oxygen is also a key effector of many developmental events. The oxygen‐sensing machinery and the very fabric of cell identity and function have been shown to be deeply intertwined. Here we take a first look at how oxygen might lie at the crossroads of at least two of the major molecular pathways that shape pancreatic development. Based on recent evidence and a thorough review of the literature, we present a theoretical model whereby evolving oxygen tensions might choreograph to a large extent the sequence of molecular events resulting in the development of the organ. In particular, we propose that lower oxygenation prior to the expansion of the vasculature may favour HIF (hypoxia inducible factor)‐mediated activation of Notch and repression of Wnt/β‐catenin signalling, limiting endocrine cell differentiation. With the development of vasculature and improved oxygen delivery to the developing organ, HIF‐mediated support for Notch signalling may decline while the β‐catenin‐directed Wnt signalling is favoured, which would support endocrine cell differentiation and perhaps exocrine cell proliferation/differentiation.     

Maintenance of photosynthesis at low leaf water potential in wheat : role of potassium status and irrigation history

The interaction of low water potential effects on photosynthesis, and leaf K⁺ levels in wheat (Triticum aestivum L.) plants was studied. Plants were grown at three K⁺ fertilization levels; 0.2, 2, and 6 millimolar. With well watered plants, 2 millimolar K⁺ supported maximal photosynthetic rates; 0.2 millimolar K⁺ was inhibitory, and 6 millimolar K⁺ was superoptimal (i.e. rates were no greater than at 2 millimolar K⁺). Photosynthesis was monitored at high (930 parts per million) and low (330 parts per million) external CO₂ throughout a series of water stress cycles. Plants subjected to one stress cycle were considered nonacclimated; plants subjected to two successive cycles were considered acclimated during the second cycle. Sensitivity of photosynthesis to declining leaf water potential was affected by K⁺ status; 6 millimolar K⁺ plants were less sensitive, and 0.2 millimolar K⁺ plants were more sensitive than 2 millimolar K⁺ plants to declining water potential. This occurred with nonacclimated and acclimated plants at both high and low assay CO₂. It was concluded that the K⁺ effect on photosynthesis under stress was not mediated by treatment effects on stomatal resistance. Differences between the K⁺ treatments were much less pronounced, however, when photosynthesis of nonacclimated and acclimated plants was plotted at a function of declining relative water content during the stress cycles. These results suggest that K⁺ effects on the relationship between relative water content and water potential in stressed plants was primarily responsible for the bulk of the K⁺-protective effect on photosynthesis in stressed plants. In vitro experiments with chloroplasts and protoplasts isolated from 2 millimolar K⁺ and 6 millimolar K⁺ plants indicated that upon dehydration, K⁺ efflux from the chloroplast stroma into the cytoplasm is less pronounced in 6 millimolar K⁺ protoplasts.     

Effects of acetylcholinesterase specific inhibitors on the development of chick embryos

The effects of specific inhibitors of cholinesterases on chick development were studied. Inhibitors were injected into the eggs, at final concentration ranging between 1 mM and 10 nM. Their effects were depending on inhibitor concentration, and detectable at stages as more advanced as more diluted were the inhibitors. The strongest teratogenic effects on gastrulation, neurulation and morphogenesis were caused by BW 284c51, specific inhibitor of acetylcholinesterase. Its effects were compared to those of ion channels blockers. The inhibitors action seems to be correlated to an altered cholinergic system and to consequently altered intercellular communications.     

Effects of cyclopiazonic acid and aflatoxin singly and in combination on selected clinical,pathological and immunological responses of guinea pigs

Cyclopiazonic acid (CPA) and aflatoxin are known sometimes to coexist in nature but little is known of possible biological interaction in mammals that consume mixtures of these two mycotoxins. Guinea pigs were dosed orally with CPA (2.2 mg/kg) or aflatoxin (0.045 mg B₁/kg) singly or in combination. Effects of toxin consumption were determined on clinical health, body weight gain, pathological change, and several immunologically related parameters including delayed cutaneous hypersensitivity, antibody response, complement hemolytic titer, intracutaneous mitogen (PHA) and in vitro lymphocyte blastogenesis. In contrast to an earlier study by others, significant synergy between these two toxins was demonstrated in reduced rate of body weight gain, lethality and histologic changes (vacuolization) in hepatocytes. Reductions in complement titer, intradermal PHA, delayed cutaneous hypersensitivity response and in vitro lymphocyte blastogenesis were related to aflatoxin activity. No effects on antibody formation to Brucella abortus were observed with either toxin or the combination of toxins. Cyclopiazonic acid appeared to restore the suppressive effects of aflatoxin in delayed cutaneous hypersensitivity response and in vitro lymphocyte blastogenesis.     

Diffusione pollinica e caratteristiche immunologiche e broncoreattive di soggetti atopici in Pietra Ligure (Savona)

Riassunto Sono state rilevate durante un monitoraggio aerobiologico effettuato a Pietra Ligure (Savona) nel corso del 1987 le concentrazioni polliniche di 50 taxa ed è stata valutata l'influenza relativa dei fattori meteorologici. Le osservazioni palinologiche sono state rapportate alle concentrazioni sieriche delle IgE specifiche, alla reattività bronchiale specifica ed aspecifica valutate in 101 pazienti allergici (rinitici ed asmatici), sensibilizzati a Graminaceae ed Urticaceae (Parietaria) al fine di riconoscere correlazioni tra le caratteristiche aerobiologiche di questi allergeni edi meccanismi patogenetici che sostengono la reattività bronchiale.