Different acute effects of the tyrosine hydroxylase inhibitors alpha-methyl-p-tyrosine and 3-iodo-L-tyrosine on hypothalamic noradrenaline activity and adrenocorticotrophin release in the rat

Computerized gas chromatography-mass spectrometry techniques using selected ion monitoring and deuterated internal standards were used to assay simultaneously the medial basal hypothalamic concentrations of dopamine (DA) and noradrenaline (NA) and their major metabolites in individual rats 30 min after the administration of two different inhibitors of tyrosine hydroxylase, alpha-methyl-p-tyrosine (alpha-MT) and 3-iodo-L-tyrosine (MIT). Consistent with inhibition of DA synthesis, administration of both alpha-MT and MIT resulted in marked reductions (P less than 0.005) in the hypothalamic concentrations of DA and its metabolite homovanillic acid as well as in highly significant increases in prolactin secretion. alpha-MT administration, but not MIT, resulted in a highly significant decrease in NA concentration and a highly significant increase in the concentration of the NA metabolite 3,4-dihydroxyphenylethyleneglycol (DHPG). The hypothalamic ratio DHPG/NA was thus markedly increased (P less than 0.005) by alpha-MT indicating increased NA neuronal activity. alpha-MT administration also resulted in increased ACTH secretion (P less than 0.0005), an effect not observed following MIT. It is proposed that the effects on hypothalamic NA activity and ACTH secretion caused by alpha-MT are stress-mediated and unrelated to tyrosine hydroxylase inhibition. MIT is devoid of these effects but exhibits blockade activity, thus indicating it to be a preferable drug for the acute inhibition of tyrosine hydroxylase in neuroendocrine investigations.     

Specific binding of covalently cross-linked mouse nerve growth factor to responsive peripheral neurons.

The binding characteristics of [¹²⁵I]nerve growth factor, covalently cross-linked with dimethyl suberimidate, to chick embryonic dorsal root ganglia are indistinguishable from the iodinated native hormone. Both show non-saturability, non-linear Scatchard plots and acceleration of dissociation of hormone-receptor complexes by native hormone which is reflected in the binding constants calculated. These results demonstrate that dimerization of the native hormone at the receptor is not responsible for the negatively cooperative behavior observed for native nerve growth factor. Further, experiments with amino-silylated glass tubes also eliminate interaction between hormone and reaction vessel as an explanation of the non-saturable and multiple affinity properties of the observed binding.     

Estimating co-extinction threats in terrestrial ecosystems

The biosphere is changing rapidly due to human endeavour. Because ecological communities underlie networks of interacting species, changes that directly affect some species can have indirect effects on others. Accurate tools to predict these direct and indirect effects are therefore required to guide conservation strategies. However, most extinction-risk studies only consider the direct effects of global change—such as predicting which species will breach their thermal limits under different warming scenarios—with predictions of trophic cascades and co-extinction risks remaining mostly speculative. To predict the potential indirect effects of primary extinctions, data describing community interactions and network modelling can estimate how extinctions cascade through communities. While theoretical studies have demonstrated the usefulness of models in predicting how communities react to threats like climate change, few have applied such methods to real-world communities. This gap partly reflects challenges in constructing trophic network models of real-world food webs, highlighting the need to develop approaches for quantifying co-extinction risk more accurately. We propose a framework for constructing ecological network models representing real-world food webs in terrestrial ecosystems and subjecting these models to co-extinction scenarios triggered by probable future environmental perturbations. Adopting our framework will improve estimates of how environmental perturbations affect whole ecological communities. Identifying species at risk of co-extinction (or those that might trigger co-extinctions) will also guide conservation interventions aiming to reduce the probability of co-extinction cascades and additional species losses.     

An Experimental Study on the Revegetation of Colliery Spoils of Bold Moss Tip,St. Helens,England

Three spoils from Bold Moss Tip, St. Helens, and one from Neston, England were collected for experiment to find the problems and solutions to reclaim the coal-mine lands of Bold Moss Tip, from seeds and tillers of Agrostis stolonifera, A. capillaris and Hocus lanatus. Low pH (3.0 to 6.8), deficient in nutrient, especially N (0. 24 to 0. 28 ppm), P(0. 016 to 6.1 ppm). and excess of Mg(>1000ppm), Na(84 to 325ppm), and Fe (>20 000ppm)were found in the spoils of Bold Moss Tip, which was supposed to be the most difficult problems of restoration. Tillers of A. stolonifera and A. capillaris could not be planted directly to the bare spoils of Bold Moss Tip, but those of vegetated spoils (Site 2 and Site 3) could support the growth of tillers. The pH value was found to be the key factor to control seed germinations of the three species, below pH 3, there were no germination. A. stolonifera and A. capillaris germinated with the highest rates (97% and 96%) at pH 5 and pH7(p<0. 01)respectively. The application of lime stone could increase spoil pH significantly (p<0. 001), from 2.2 to 7. 3, when 40 t·ha-1 lime stone was added. Lime stone had the best effect to the four spoils. Lime stone +NP significantly increased the yield of dry matters of Site 2 (p<0. 001); The highest yield, 735.6 g · m-1, was gained from the treatment of spoils of Neston with lime stone + N; Lime could also increase the yield of Site 1 from 0 to 125. l g·m-1(p<0. 05). Gypsum had some effect to spoils of Site 2 and Neston, compared with the bland treatment, but did no influence to the spoils of Site 1. Washing had minimum effect toward the spoils of Site 2, and showed no effect to Site 1 and Neston; Throughout the 8-weed% experiment there was little change in the pH of Site 1, even though the spoils were washed everyday. Fertilisers alone had no effect to the bare spoils of Bold Moss Tip, and Neston, but they could enhance the growth of seedling of Site 2, however together with lime stone, the role of fertilisers were significant (p<0. 001). Both nitrogen and phosphorus were essential to the spoils of Bold Moss Tip . Without top-soils, the bare of Bold Moss Tip can be revegetated only by application of lime stone, but better effect coult be obtained by addition of nitrogen and phosphorus. The rates of 20 to 60 t·ha-1, 75 kg N ha-1 and 50 kg P ha-1 of lime stone, nitrogen, phosphorus respectively, are suggested for application.     

Relative feeding and development of armyworm on switchgrass and corn, and its potential effects on switchgrass grown for biomass

To help assess the potential for damage by armyworms [Mythimna (Pseudaletia) unipuncta (Haworth) (Lepidoptera: Noctuidae)] to switchgrass (Panicum virgatum L.) and surrounding crops, survival and development were evaluated for larvae reared on leaves of switchgrass, corn (Zea mays L.), and miscanthus (Miscanthus x giganteus Greef and Deuter ex Hodkinson and Renvoize). Additional tests assessed the relationship between leaf position and the concentration of saponins (plant compounds which can provide protection from insect herbivores) and examined the effect of defoliation on switchgrass dry mass. Survival to adulthood was similar when larvae were reared on field-grown leaves of switchgrass and corn. However, lower larval mass (10 d) and delayed development of M. unipuncta (to pupation, adult emergence) suggest switchgrass is an inferior host relative to corn. When fed field-grown miscanthus, no larvae survived 10 d. Few differences were noted between switchgrass and corn grown under controlled (laboratory) conditions, but M. unipuncta survival seemed to decline rapidly when larvae were fed the fourth and fifth leaves of switchgrass. Switchgrass leaf samples collected from different leaf positions and stages of tiller maturity showed up to 10-fold differences in the concentration of the saponin protodioscin, with the greatest concentrations in the fourth and fifth leaves. However, other saponins showed an opposite pattern, indicating the role of protodioscin on insect development should be tested in isolation (e.g., by addition of the purified compound to an artificial diet). Defoliation trials indicated that extremely high M. unipuncta populations may be necessary to cause any significant reduction in switchgrass biomass. Collectively, results suggest M. unipuncta may not present a significant risk to biomass production in switchgrass, but that the spring emergence of switchgrass provides an alternate host for M. unipuncta before colonizing annual food and feed crops.     

A structural study of the myristoylated N-terminus of ARF1

The effect of myristoylation on the 15-amino-acid peptide from the membrane-binding N-terminus of ADP ribosylation factor 1 (ARF1) was studied using neutron diffraction and circular dichroism. A previous study on the non-acylated form indicated that the peptide lies parallel to the membrane, at a shallow depth and in the vicinity of the phosphorylcholine headgroups. It was suggested that the helix does not extend past residue 12, an important consequence for the linking region of the ARF1 protein. In this paper, we show that the result of myristoylation is to increase the helical content reaching the peptide's C-terminus, resulting in the formation of a new hydrophobic face. This increased helicity may augment the entire protein's membrane-binding affinity, indicating that ARF1 effectively has two interdependent membrane-binding motifs.     

Amino acid sequence of guinea pig prostate kallikrein

The primary structure of the major arginine esteropeptidase from guinea pig prostate has been deduced from automated Edman degradation of peptides generated by clostripain, cyanogen bromide, endoproteinase Lys-C, and Staphylococcus aureus V8 protease digestion of the protein. The esteropeptidase is a single polypeptide chain comprised of 239 amino acids and contains 2 apparent sites of carbohydrate attachment, Asn-78 and Asn-169. Both occur in consensus sequences for N-linked glycosylation sites. The esteropeptidase exhibits approximately 35% homology with trypsin including conservation of the catalytic residues and the aspartic acid which confers specificity toward basic amino acids. The sequence identity, however, extends to greater than 60% with the kallikrein family of serine proteases. In addition to the overall homology, the guinea pig enzyme displays a number of features characteristic of kallikreins including 10 conserved half-cystine residues, a C-terminal proline, and the "kallikrein loop". On the basis of this structural relatedness, the enzyme has been designed as guinea pig prostate kallikrein. In contrast to many of the kallikreins of other species and tissues, this enzyme does not contain any sites within the kallikrein loop sensitive to proteases that result in internal breaks in the polypeptide chain.