Activation of integrin alphaIIbbeta3 by modulation of transmembrane helix associations

Transmembrane helices of integrin alpha and beta subunits have been implicated in the regulation of integrin activity. Two mutations, glycine-708 to asparagine-708 (G708N)and methionine-701 to asparagine-701, in the transmembrane helix of the beta3 subunit enabled integrin alphaIIbbeta3 to constitutively bind soluble fibrinogen. Further characterization of the G708N mutant revealed that it induced alphaIIbbeta3 clustering and constitutive phosphorylation of focal adhesion kinase. This mutation also enhanced the tendency of the transmembrane helix to form homotrimers. These results suggest that homomeric associations involving transmembrane domains provide a driving force for integrin activation. They also suggest a structural basis for the coincidence of integrin activation and clustering.     

Determination of the equation of state of dense matter

Nuclear collisions can compress nuclear matter to densities achieved within neutron stars and within core-collapse supernovae. These dense states of matter exist momentarily before expanding. We analyzed the flow of matter to extract pressures in excess of 10(34) pascals, the highest recorded under laboratory-controlled conditions. Using these analyses, we rule out strongly repulsive nuclear equations of state from relativistic mean field theory and weakly repulsive equations of state with phase transitions at densities less than three times that of stable nuclei, but not equations of state softened at higher densities because of a transformation to quark matter.     

Control of ion transport by the sperm duct epithelium of brook trout (Salvelinus fontinalis)

The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na⁺ (measured as the short-circuit current, I_sc) and secretes K⁺ (measured using⁸⁶Rb⁺ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na⁺ uptake and K⁺ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor (chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results suggest direct involvement of GtH in control of later stages of sperm maturation.     

Correlation of fluridone and dye concentrations in water following concurrent application

Herbicide residue samples are expensive and time-consuming to collect and analyze. To test whether Rhodamine WT dye could simulate the dissipation of fluridone, concurrent applications of the chemicals were made in the weed-infested Three Sisters tidal canals (Citrus Co. Fl) and a shallow lake in the Upper St Johns River, Florida. Dye concentrations were measured using a field fluorometer and fluridone concentrations were analyzed by an HPLC method. The coefficient of correlation between dye and herbicide was 0.99 in the canals and 0.93 in Lake Hell ‘n’ Blazes (Upper St Johns River) over 340 and 93 h respectively. Half-lives of the chemicals were not significantly different for either site. The importance of these data in relation to herbicide registration is discussed.     

The physical and chemical properties of the herbicide cinmethylin (SD 95481)

Cinmethylin (SD 95481), is a novel herbicide developed for the selective pre-emergence control of many annual grass weeds in a wide range of temperate and tropical crops. Representing new herbicide chemistry, cinmethylin is in the cineole family. Cinmethylin is a mobile colourless liquid with a boiling point of 313°C under an inert atmosphere at atmospheric pressure. It has a density of 1015 kg m^?3 and a viscosity of 70–90 mPa s, both at 20°C. It is miscible in all proportions with most organic solvents but has a low solubility, 63 mg litre^?1, in water. It has a vapour pressure of 10.2 mPa (20°C) and the vapour pressure/temperature relationship is given by log_e P(Pa)=28.9–9816/T (K). The n-octanol/water partition coefficient is 6850 and soil organic matter/water sorption coefficient (K_om) ranges between 165 and 235 over the three types of soil used in these studies. Cinmethylin is stable in water over the pH range 3–11. Solutions of cinmethylin in water or solvents are reasonably stable to sunlight, though thin films on a quartz surface photooxidise mainly to an ester within 24 h. This rate can be reduced by the addition of photostabilisers or by sorption onto soil surfaces. In an inert atmosphere cinmethylin is stable to high temperatures, though, in air, oxidation occurs at temperatures above 100°C to give the same product as by photodecay.     

Esterase isozymes in Lygus hesperus: Characterization and relationship with organophosphate resistance

Esterases of Lygus hesperus Knight from five field and one laboratory populations were separated by non-denaturing polyacrylamide gel electrophoresis and were characterized for inhibition and substrate specificity. There were six zones of esterase activity toward naphthyl ester substrates. Significant inter- and intra-populational polymorphisms were observed. All the isozymes were carbo-xylesterases that were sensitive to inhibition by paraoxon and insensitive to eserine or EDTA (ethylenedinitrilotetraacetic acid). Carboxylesterases from L. hesperus more readily hydrolysed naphthyl esters with short side chains. Molecular weight estimation by non-denaturing polyacrylamide gel electrophoresis revealed that Est-1, the specific band of older females and eggs, contained two enzymes with relative molecular masses of 140000 and 112000. The four esterase allozymes in Est-3 had an average relative molecular mass of approximately 106000. The frequency of one putative allozyme in Est-3 was directly correlated with the LC₅₀ values of trichlorfon (to which L. hesperus has become resistant). The developmental and distribution variability of the esterase isozymes are compared.     

Measurement of acephate and its principal metabolite in leaves by gas-liquid chromatography

A semi-micro method is described for monitoring levels of acephate (O, S-dimethyl acetylphosphoramidothioate) and its principal metabolite, methamidophos (O, S-dimethyl phosphoramidothioate) in leaf material derived from treated, hydroponically grown gerberas (Gerbera jamesonii H. Bollus, ex Hook. f.) To minimise injury to the living leaf, analyses were performed on 13-mm diameter discs punched from the interveinal regions of the lamina. The leaf disc samples were then extracted with ethyl acetate. Clean-up of extracts was accomplished by passing the filtered leaf extracts through glass mini-columns containing carbon + filter aid (2 + 5 by mass). Acephate and methamidophos were eluted from the column with methanol and measured simultaneously by programmed temperature gas chromatography using a thermionic specific detector.     

Nonendoscopic Antegrade Percutaneous Gastrostomy: The Effect of Preplacement Gastric Insufflation on Tube Position and Intra-Abdominal Anatomy

Nonendoscopic tube gastrostomy was performed on 41 anesthetized dogs using the technique of Fulton and Dennis with or without gastric insufflation prior to tube placement. Immediately after tube placement, dogs were euthanized and postmortem examinations performed. When gastric insufflation was not performed (group I), gastrostomy tubes penetrated the visceral surface of the stomach in 25% of dogs. The deep leaf of the omentum was interposed between stomach and body wall in the majority of these dogs, exposing other intra-abdominal organs to potential injury. Additionally, displacement and tethering of the spleen cranial to the gastrostomy site were observed in 33% of dogs in group I. Similar results were obtained when preplacement gastric insufflation was performed after the orogastric tube was inserted sufficiently far to displace the stomach laterally against the body wall (group II). In contrast, consistent positioning of gastrostomy tubes through the parietal surface of the stomach was achieved when the stomach was insufflated prior to lateralizing the left abdominal wall with the gastric end of the orogastric tube (group III). It was concluded that the blind percutaneous gastrostomy technique is made safer by insufflating the stomach immediately prior to pushing the gastric wall laterally into contact with the parietal peritoneum. J Vet Intern Med 1996;10:15–20. Copyright © 1996 by the American College of Veterinary Internal Medicine .