Cell swelling induced by the permeant molecules urea or glycerol induces immediate high amplitude thyrotropin and prolactin secretion by perifused adenohypophyseal cells

The permeant molecules, urea and glycerol, evoked a prompt secretory burst of TSH and PRL when added to the extracellular medium of acutely dispersed anterior pituitary cells. Secretion of both hormones was proportional to the concentration of urea or glycerol between 26 and 104 mM (r greater than 0.89, P less than 0.001). Equivalent concentrations of the impermeant molecule, mannitol, did not induce secretion. The acute TSH and PRL secretory responses to TRH, hyposmolarity, and permeant molecules were qualitatively indistinguishable. These data support our hypothesis that cell swelling and resultant plasmalemma expansion is a potent inducer of hormone secretion. Since the secretory response to permeant molecules was not reduced in a Ca2+-free medium containing 0.1 mM EGTA, an increase in Ca2+ transport across the plasmalemma to raise cytosol Ca2+ concentration does not appear involved.     

Hydroxyl Radical-Mediated Oxidation of Serotonin: Potential Insights into the Neurotoxicity of Methamphetamine

Abstract: When incubated with a hydroxyl radical (HO^?)-generating system (ascorbic acid/Fe²⁺-EDTA/O₂/H₂O₂), 5-hydroxytryptamine (5-HT; serotonin) is rapidly oxidized initially to a mixture of 2,5-, 4,5-, and 5,6-dihydroxytryptamine (DHT). The major reaction product is 2,5-DHT, which at physiological pH exists as its keto tautomer, 5-hydroxy-3-ethylamino-2-oxindole (5-HEO). Rapid autoxidation of 4,5-DHT gives tryptamine-4,5-dione (T-4,5-D), which reacts with the C(3)-centered carbanion of 5-HEO to give 3,3′-bis(2-aminoethyl)-5-hydroxy-[3,7′-bi-1H-indole]-2,4′,5′-3H-trione (7). The latter slowly cyclizes to 3′-(2-aminoethyl)-1′,6′,7′,8′-tetrahydro-5-hydroxyspiro[3H-indole-3,9′-[9H]pyrrolo[2,3-f]quinoline]-2,4′,5′(1H)- trione (9). A minor amount of T-4,5-D dimerizes to give 7,7′-bi-(5-hydroxytryptamine-4-one) (7,7′-D). In the presence of GSH, the reaction of T-4,5-D with 5-HEO is diverted and, in the presence of sufficient concentrations of this tripeptide, completely blocked. This is because GSH preferentially reacts with T-4,5-D to give 7-S-glutathionyltryptamine-4,5-dione (11). The results of this investigation suggest that 5,6-DHT, 5-HEO, 7, and 9 are products unique to the HO^?-mediated oxidation of 5-HT. Thus, the observation of other investigators that 5,6-DHT is formed in the brains of rats following a large dose of methamphetamine (MA) suggests that this drug might evoke HO^? formation. However, the present in vitro study indicates that 5,6-DHT is a rather minor, unstable product of the HO^?-mediated oxidation of 5-HT and suggests that detection of 5-HEO, 7/9, and 11 in rat brain following MA administration could provide additional support for HO^? formation. Furthermore, one or more of the intermediates and major products of oxidation of 5-HT by HO^? might, in addition to 5,6-DHT, contribute to the MA-induced degeneration of serotonergic neurons.     

Direct interaction of resistance gene and avirulence gene products confers rice blast resistance

Rice expressing the Pi-ta gene is resistant to strains of the rice blast fungus, Magnaporthe grisea, expressing AVR-Pita in a gene-for-gene relationship. Pi-ta encodes a putative cytoplasmic receptor with a centrally localized nucleotide-binding site and leucine-rich domain (LRD) at the C-terminus. AVR-Pita is predicted to encode a metalloprotease with an N-terminal secretory signal and pro-protein sequences. AVR-Pita(176) lacks the secretory and pro-protein sequences. We report here that transient expression of AVR-Pita(176) inside plant cells results in a Pi-ta-dependent resistance response. AVR-Pita(176) protein is shown to bind specifically to the LRD of the Pi-ta protein, both in the yeast two-hybrid system and in an in vitro binding assay. Single amino acid substitutions in the Pi-ta LRD or in the AVR-Pita(176) protease motif that result in loss of resistance in the plant also disrupt the physical interaction, both in yeast and in vitro. These data suggest that the AVR-Pita(176) protein binds directly to the Pi-ta LRD region inside the plant cell to initiate a Pi-ta-mediated defense response.     

Towards a circuit engineering discipline

Genetic circuits can now be engineered that perform moderately complicated switching functions or exhibit predictable dynamical behavior. These 'forward engineering' techniques may have to be combined with directed evolution techniques to produce robustness comparable with naturally occurring circuits.     

Monocytes/macrophages express chemokine receptor CCR9 in rheumatoid arthritis and CCL25 stimulates their differentiation

Introduction  

Monocytes/macrophages accumulate in the rheumatoid (RA) synovium where they play a central role in inflammation and joint destruction. Identification of molecules involved in their accumulation and differentiation is important to inform therapeutic strategies. This study investigated the expression and function of chemokine receptor CCR9 in the peripheral blood (PB) and synovium of RA, non-RA patients and healthy volunteers.     

Left ventricular hypertrophy is prevalent in Sprague-Dawley rats

Unrecognized cardiovascular abnormalities may confound the interpretation of research data collected using rats. However, although SPF rat colonies are screened for microbes and kept under standardized environmental conditions, their cardiovascular status is largely unknown. We recently performed surgery on anesthetized 80-d-old Sprague-Dawley rats and observed a high mortality that could not be attributed to the procedures or preceding treatments. Upon necropsy, cardiomyopathy was readily apparent in a substantial proportion of these rats. To further evaluate the nature of this condition, we evaluated the histology and morphology of hearts from both Sprague-Dawley and Lewis rats. Compared with Lewis rats, Sprague-Dawley rats had greater left ventricular wall thickness and larger cardiomyocyte cell size. Severe left ventricle hypertrophy was present in 38% of young adult Sprague-Dawley rats. These findings may have implications for research models that use Sprague-Dawley rats.     

Transcriptional profiling of Caulobacter crescentus during growth on complex and minimal media

Microarray analysis was used to examine gene expression in the freshwater oligotrophic bacterium Caulobacter crescentus during growth on three standard laboratory media, including peptone-yeast extract medium (PYE) and minimal salts medium with glucose or xylose as the carbon source. Nearly 400 genes (approximately 10% of the genome) varied significantly in expression between at least two of these media. The differentially expressed genes included many encoding transport systems, most notably diverse TonB-dependent outer membrane channels of unknown substrate specificity. Amino acid degradation pathways constituted the largest class of genes induced in PYE. In contrast, many of the genes upregulated in minimal media encoded enzymes for synthesis of amino acids, including incorporation of ammonia and sulfate into glutamate and cysteine. Glucose availability induced expression of genes encoding enzymes of the Entner-Doudoroff pathway, which was demonstrated here through mutational analysis to be essential in C. crescentus for growth on glucose. Xylose induced expression of genes encoding several hydrolytic exoenzymes as well as an operon that may encode a novel pathway for xylose catabolism. A conserved DNA motif upstream of many xylose-induced genes was identified and shown to confer xylose-specific expression. Xylose is an abundant component of xylan in plant cell walls, and the microarray data suggest that in addition to serving as a carbon source for growth of C. crescentus, this pentose may be interpreted as a signal to produce enzymes associated with plant polymer degradation.