Topographical distribution of CRF immunoreactivity in the pigeon brain

The distribution of corticotropin-releasing factor (CRF) immunoreactivity was demonstrated by immunocytochemistry in intact and colchicine-treated pigeons. Colchicine injections were administered at different times related to the circadian activity of the CRF-adrenocorticotropin (ACTH)-corticosterone axis. Three CRF antisera were used, two directed against synthetic rat CRF and one directed against synthetic ovine CRF. No fundamental differences appeared in the pigeon brain with respect to the specific CRF antiserum used. The most effective colchicine injection times corresponded to hypersecretion in the corticotropic axis. CRF-immunopositive neurons were scattered throughout the pigeon brain. In addition to the paraventricular hypothalamic system, which is involved in adenohypophysial ACTH regulation, several other hypothalamic and extrahypothalamic areas showed CRF neurons. The distribution suggests that CRF may also act as a modulator and a neurotransmitter. Two hypothalamic paraventricular nucleus-median eminence CRF pathways are described here. Moreover, CRF-immunopositive reactions were observed in specific areas of cerebral ventricle walls, suggesting that CRF may be released into the cerebral fluid.     

Temperature effect on subclasses of muscarinic receptors in rat colon, heart and cerebral cortex

The high-affinity muscarinic antagonist /3H/-Quinuclidinyl benzilate (/3H/-QNB) has been used to label muscarinic receptors in a crude membrane fraction of rat cerebral cortex, colon and heart. The inhibition of /3H/-QNB binding by Atropine, Oxotremorine and Pirenzepine was investigated at three temperatures: 37 degrees C, 22 degrees C and 10 degrees C. The IC50 values and the proportion of high (Rt1) and low (Rt2) affinity binding sites were determined for the three compounds. When the temperature were lowered from 37 degrees C to 10 degrees C, in the agonist and antagonist dissociation constants decreased in all tissues. Changes in temperature did not modify Rt1 or Rt2 values for Oxotremorine and Pirenzepine. The results show marked temperature-dependent modifications of IC50 values for muscarinic receptors of high- and low-affinity sites in rat cerebral cortex, colon or heart.     

Assessment of TRH as a potential MSH release stimulating factor in Xenopus laevis

This study considers the possible involvement of the tripeptide TRH (thyrotropin releasing hormone) in the physiological regulation of melanophore stimulating hormone (MSH) secretion from the pars intermedia of the toad, Xenopus laevis. TRH was shown to stimulate release of MSH from superfused neurointermediate lobes obtained from white-background adapted animals, but had no effect on secretion from lobes of black-background adapted animals. Immunohistochemical analysis revealed a rich TRH-containing neuronal network terminating in the neural lobe of the Xenopus pituitary. Plasma levels of TRH, determined with a specific radioimmunoassay, proved to be extremely high and no significant difference in this level could be found between white- and black-adapted animals. Plasma TRH probably originates from the skin, and our results show that its concentration is within the effective concentration range established for this peptide in stimulating MSH release from the pars intermedia. Therefore, while both our superfusion and immunohistochemical results argue favourably for a function of TRH in the regulation of MSH secretion, we conclude that, in any regulatory role, it would likely have to function within the pars intermedia at concentrations exceeding the high plasma values. While TRH could be involved in short-term activation of the secretory process in white-background adapted animals or in animals undergoing the initial stages of black background adaptation, our results indicate that this peptide may have no function in the maintenance of secretion from the pars intermedia of animals fully adapted to black background.     

Influence of endogenous growth hormone-releasing factor (GRF) on the secretion of GH during the perinatal period in the rat

Passive immunization of pregnant rats with a specific antiserum to rat GRF (GRF-AS) is followed by a decrease in fetal serum GH on the 19th day of gestation. A significant reduction in serum GH is still observed in older fetuses and newborn rats. Pituitary GH content increases in 19- and 20-day-old fetuses after GRF-AS administration to their mothers. These results suggest that endogenous fetal hypothalamic GRF (or placenta GRF) play a physiological role in the secretion of pituitary GH as early as the 19th day of fetal life and may be responsible for the peak of GH release that occurs in fetuses at the end of gestation.     

RNA Isolation method for polysaccharide rich algae: agar producing <Emphasis Type="Italic">Gracilaria tenuistipitata</Emphasis> (Rhodophyta)

RNA isolation is essential to study gene expression at the molecular level. However, RNA isolation is difficult in organisms (plants and algae) that contain large amounts of polysaccharides, which co-precipitate with RNA. Currently, there is no commercial kit available, specifically for the isolation of high-quality RNA from these organisms. Furthermore, because of the large amounts of polysaccharides, the common protocols for RNA isolation usually result in poor yields when applied to algae. Here we describe a simple method for RNA isolation from the marine red macroalga Gracilaria tenuistipitata var. liui Zhang et Xia (Rhodophyta), which can be applied to other plants and algae.     

Biochar mineralization and priming effect on SOM decomposition in two European short rotation coppices

As studies on biochar stability in field conditions are very scarce, the carbon sequestration potential of biochar application to agricultural soils remains uncertain. This study assessed the stability of biochar in field conditions, the effect of plant roots on biochar stability and the effect of biochar on original soil organic matter (SOM) decomposition in two (Italy and United Kingdom) short rotation coppice systems (SRCs), using continuous soil respiration monitoring and periodic isotopic (δ¹³CO₂) measurements. When root growth was excluded, only 7% and 3% of the biochar carbon added was decomposed after 245 and 164 days in Italy and United Kingdom sites respectively. In the presence of roots, this percentage was increased to 9% and 8%, suggesting a small positive priming effect of roots on biochar decomposition. A decreased decomposition rate of original SOM was observed at both sites after biochar incorporation, suggesting a protective effect of biochar on SOM. This study supports the carbon sequestration potential of biochar and highlights the role of root activity on biochar decomposition, questioning the applicability of laboratory incubation studies to assess biochar stability.