DNA sequences from Arabidopsis, which encode protein kinases and function as upstream regulators of Snf1 in yeast

Sucrose nonfermenting-1 (Snf1)-related protein kinase-1 (SnRK1) of plants is a global regulator of carbon metabolism through the modulation of enzyme activity and gene expression. It is structurally and functionally related to the yeast protein kinase, Snf1, and to mammalian AMP-activated protein kinase. Two DNA sequences from Arabidopsis thaliana, previously known only by their data base accession numbers of NM_ 125448.3 (protein ID NP_200863) and NM_114393.3 (protein ID NP_566876) each functionally complemented a Saccharomyces cerevisiae elm1 sak1 tos3 triple mutant. This indicates that the Arabidopsis proteins are able to substitute for one of the missing yeast upstream kinases, which are required for activity of Snf1. Both plant proteins were shown to phosphorylate a peptide with the amino acid sequence of the phosphorylation site in the T-loop of SnRK1 and by inference SnRK1 in Arabidopsis. The proteins encoded by NM_125448.3 and NM_114393.3 have been named AtSnAK1 and AtSnAK2 (Arabidopsis thaliana SnRK1-activating kinase), respectively. We believe this is the first time that upstream activators of SnRK1 have been described in any plant species.     

Apical cell protrusions cause vertical deformation of the soft cancer nucleus

Breast cancer nuclei have highly irregular shapes, which are diagnostic and prognostic markers of breast cancer progression. The mechanisms by which irregular cancer nuclear shapes develop are not well understood. Here we report the existence of vertical, apical cell protrusions in cultured MDA-MB-231 breast cancer cells. Once formed, these protrusions persist over time scales of hours and are associated with vertically upward nuclear deformations. They are absent in normal mammary epithelial cells (MCF-10A cells). Microtubule disruption enriched these protrusions preferentially in MDA-MB-231 cells compared with MCF-10A cells, whereas inhibition of nonmuscle myosin II (NMMII) abolished this enrichment. Dynamic confocal imaging of the vertical cell and nuclear shape revealed that the apical cell protrusions form first, and in response, the nucleus deforms and/or subsequently gets vertically extruded into the apical protrusion. Overexpression of lamin A/C in MDA-MB-231 cells reduced nuclear deformation in apical protrusions. These data highlight the role of mechanical stresses generated by moving boundaries, as well as abnormal nuclear mechanics in the development of abnormal nuclear shapes in breast cancer cells.     

Motivational control of caching behaviour in the scrub jay, Aphelocoma coerulescens

We investigated the motivational control of caching behaviour in scrub jays using a two-stage procedure to examine the effects of prefeeding and/or precaching (stage 1) on subsequent caching behaviour (stage 2). Experiment 1 demonstrated that both prefeeding and precaching reduced the subsequent caching of both edible (peanuts) and inedible (stones) items. The reduction in caching was greatest when the items available for storing were the same in the two stages. This item specificity was confirmed in experiment 2 using two food types, peanuts and dog food kibbles. The final experiment demonstrated that the effect of prefeeding on subsequent caching can also be food specific, in that birds that received food in a powdered form that they could eat, but not cache in stage 1, showed a reduction in subsequent caching in stage 2 only when the food type was the same in the two stages. These results suggest that caching behaviour is controlled by both the feeding system and an independent caching system, and that this control is mediated by the incentive value of the specific items rather than by a general motivational state. Copyright 1999 The Association for the Study of Animal Behaviour.     

Neural crest cell lineage segregation in the mouse neural tube

Neural crest (NC) cells arise in the dorsal neural tube (NT) and migrate into the embryo to develop into many different cell types. A major unresolved question is when and how the fate of NC cells is decided. There is widespread evidence for multipotential NC cells, whose fates are decided during or after migration. There is also some evidence that the NC is already divided into subpopulations of discrete precursors within the NT. We have investigated this question in the mouse embryo. We find that a subpopulation of cells on the most dorsomedial aspect of the NT express the receptor tyrosine kinase Kit (previously known as c-kit), emigrate exclusively into the developing dermis, and then express definitive markers of the melanocyte lineage. These are thus melanocyte progenitor cells. They are generated predominantly at the midbrain-hindbrain junction and cervical trunk, with significant numbers also in lower trunk. Other cells within the dorsal NT are Kit-, migrate ventrally, and, from embryonic day 9.5, express the neurotrophin receptor p75. These cells most likely only give rise to ventral NC derivatives such as neurons and glia. The p75+ cells are located ventrolateral to the Kit+ cells in areas of the NT where these two cell types are found. These data provide direct in vivo evidence for NC lineage segregation within the mouse neural tube.     

Coordinated gastric and sphincter motility evoked by intravenous CCK-8 as monitored by ultrasonomicrometry in rats

Gastric and sphincter motility evoked by intravenous injection of CCK-8 were investigated in urethane-anesthetized rats. Digital ultrasonomicrometry was used to monitor pyloric (PYL), antral (ANT), corpus (COR), and lower esophageal sphincter (LES) movements while simultaneously measuring intragastric pressure (IGP) and, in some experiments, subdiaphragmatic intraesophageal pressure (sIEP). Intracrystal distances (ICD) were measured continuously between pairs of piezoelectric crystals affixed to the serosa of PYL, ANT, COR (circular and longitudinal), and LES. Consecutive intravenous injections of CCK-8 (0.3, 1, and 3 microg/kg) at 30-min intervals caused dose-dependent simultaneous tonic contractions of PYL and ANT, LES opening, and drops in IGP with peak changes at 3 microg/kg of -17.9 +/- 2.1, -7.7 +/- 2.5, 6.5 +/- 1.4, and -29.2 +/- 3.8%, respectively, whereas intravenous saline had no effect. Rhythmic contractile activity was inhibited by CCK-8. COR responses were not significantly different from vehicle controls for most metrics, and the direction of response for circular COR varied between preparations, although not for repeated trials in a single preparation. During the LES response to CCK-8, sIEP rose in parallel with drops in IGP, indicating formation of a common cavity. Recovery of LES ICD after intravenous CCK occurred more rapidly than recovery of PYL ICD, suggesting the importance of preventing simultaneous patency of gastroesophageal and gastroduodenal passages. The CCK(A) receptor antagonist devazepide (500 microg/kg intravenous) inhibited motion responses evoked by intravenous CCK-8. These data revealed CCK-8-induced gastric and sphincter activity consistent with retropulsion of gastric content.     

Central and peripheral changes in catecholamine biosynthesis and turnover in rats after a short period of ozone exposure

We investigated in rat the effects of ozone exposure (0.7 ppm) for 5 h on the catecholamine biosynthesis and turnover in sympathetic efferents and various brain areas. For this purpose, the activity of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, was assessed in superior cervical ganglia and in two major noradrenergic cell groups, A2 and A6 (locus coeruleus). Tyrosine hydroxylase activity was estimated in vivo by measuring the accumulation of l-dihydroxyphenylalanine after pharmacological blockade of L-aromatic acid decarboxylases by NSD-1015 (100 mg/kg i.p.). The catecholamine turnover rate was measured after inhibition of tyrosine hydroxylase by alpha-methyl-para-tyrosine (AMPT, 250 mg/kg, i.p., 2.5 h) in peripheral sympathetic target organ (heart and lungs) as well as in some brain catecholamine terminal areas (cerebral cortex, hypothalamus and striatum). Ozone caused differential effects according to the structure. Catecholamine biosynthesis was stimulated in superior cervical ganglia (+44%, P < 0.05) and caudal A2 subset (+126%, P < 0.01), whereas catecholamine turnover was increased in heart (+183%, P < 0.01) and cortex (+22%, P < 0.05). On the other hand, catecholamine turnover was inhibited in lungs (-53%, P < 0.05) and striatum (-24%, P < 0.05). A brief exposure to ozone, at a concentration chosen to mimic pollution level encountered in urban areas, can modulate catecholamine biosynthesis and utilization rate in the sympathetic and central neurones.