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A thermodynamic investigation of the Claisen rearrangement of chorismate^2-(aq) to prephenate^2-(aq) has been performed using microcalorimetry and high-performance liquid chromatography. The study used a well-characterized monofunctional chorismate mutase from Bacillus subtilis that was devoid of prephenate dehydrogenase and prephenate dehydratase activities. The calorimetric measurements led to a standard molar enthalpy change %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% = −(55.4 ± 2.3) kJ mol^-1 at 298.15 K for this reaction. An estimated value of the standard molar entropy change %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%S%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% = 3 J K^-1 mol^-1 for the above reaction was used together with the experimental value of %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% to obtain a standard molar Gibbs free energy change %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%G%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% ≈ −56 kJ mol^-1 and an equilibrium constant K ≈ 7 × 10⁹ for the conversion of chorismate^2-(aq) to prephenate^2-(aq) at 298.15 K. Thus, for all practical purposes, this reaction can be considered to be “irreversible”. Quantum mechanics (Gaussian 94 with a B3LYP functional and a 6-31G* basis set) was used to calculate values of absolute and relative energies for the chorismic acid and prephenic acid species having charge numbers 0 and −2 both in the gas phase and in aqueous solution. The structures of prephenic acid and its dianion were also obtained along with values of thermodynamic reaction quantities. The effects of water solvation and solvent polarization were accounted for by using a self-consistent isodensity polarized continuum model (SCI-PCM). The calculated value of %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% for the conversion of chorismate^2-(aq) to prephenate^2-(aq) at 298.l5 K was −46.4 kJ mol^-1. This very good agreement between theory and experiment suggests that the energetics of this Claisen rearrangement are well understood and that the SCI-PCM method is capable of adequately describing the increased solvent−solute interaction of prephenate^2- relative to chorismate.^2-

Regulation of the expression of the histidase coded by hutk of Klebsiella aerogenes in Salmonella typhimurium and in Escherichia coli and of the expression of the histidase coded by huts of S. typhimurium in E. coli was investigated. The hutk histidase was found to be sensitive to catabolite repression in K. aerogenes and in E. coli, but insensitive to catabolite repression in S. typhimurium; huts histidase has previously been shown to be catabolite sensitive in all three organisms. The expression of both hutk and huts histidase in E. coli was activated by nitrogen starvation. Apparently, the glutamine synthetase of E. coli may activate the formation of some glutamate- and ammonia-producing enzymes.

P1-sensitive mutants of Klebsiella aerogenes were isolated and the gene order of the hut region was then determined using P1-mediated transduction. The genes are located in the Klebsiella chromosome between gal and bio as in Salmonella typhimurium. The gene order, gal, hutI, hutG, hutC, huU, hutH, bio is also the same as that observed in S. typhimurium.

3T3 cells have a large, pericellular coat which contains 30 times more hyaluronate than the amount of cell surface hyaluronate associated with simian virus 40-transformed 3T3 (SV-3T3) cells. On the other hand, SV-3T3 cells have high affinity binding sites for exogenously added hyaluronate, whereas 3T3 cells have much lower affinity sites. Removal of cell surface hyaluronate from SV-3T3 cells by treatment with hyaluronidase caused a reproducible increase in their maximum binding capacity for exogenous hyaluronate but no significant change in binding affinity or specificity. For 3T3 cells, however, the maximum amount of binding decreased and the affinity of binding increased after hyaluronidase treatment. When endogenous cell surface hyaluronate was labeled metabolically and then the cells incubated in the presence of exogenous unlabeled hyaluronate, the labeled cell surface hyaluronate was quantitatively displaced from the SV-3T3 cells but was not displaced from the 3T3 cells. Chondroitin sulfate and heparin did not displace cell surface hyaluronate from either cell type. Membranes isolated from SV-3T3 cells bound hyaluronate specifically and with high affinity, whereas membranes from 3T3 cells did not consistently bind a significant amount of hyaluronate. We conclude from these studies that the retention of endogenous hyaluronate on the surface of SV-3T3 cells is mediated by binding sites similar to those detected by the addition of exogenous hyaluronate, and the mechanism of retention of endogenous hyaluronate on the surface of 3T3 cells differs from SV-3T3 cells.

Amorphization of (100) silicon has been studied during elevated-temperature implantation with keV heavy ions. The amorphization process is very sensitive to the balance between defect production and annihilation rates, the latter resulting from dynamic annealing during ion bombardment. Amorphous-phase production is shown to depend critically on the ion dose rate. Further measurements have indicated that the amorphous phase can be difficult to nucleate at elevated temperatures, requiring the presence of existing interfaces, surfaces or crystal defects to provide appropriate nucleation sites.

A thermodynamic investigation of the conversion of chorismate^2-(aq) to {pyruvate^-(aq) + 4-hydroxybenzoate^-(aq)} has been performed by using microcalorimetry and high-performance liquid chromatography. The study used a genetically engineered sample of chorismate lyase that was prepared with the Escherichia coli ubiC gene. The calorimetric measurements led to a standard molar enthalpy change %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% = −(144 ± 7) kJ mol^-1 for this reaction at the temperature T = 298.15 K and ionic strength Im = 0. An estimated value of the standard molar entropy change %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%S%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% = 222 J K^-1 mol^-1 for the above reaction was used together with the experimental value of %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% to obtain a standard molar Gibbs free energy change %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%G%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% ≈ −210 kJ mol^-1 and an equilibrium constant K ≈ 10³⁷ for the conversion of chorismate^2-(aq) to {pyruvate^-(aq) + 4-hydroxybenzoate^-(aq)} at T = 298.15 K and Im = 0. Quantum mechanics (Gaussian 94 with a B3LYP functional and a 6-31G* basis set) was used to calculate values of absolute energies for the neutral and ionic species pertinent to this reaction both in the gas phase and in aqueous solution. The bond angles and bond lengths in pyruvic acid and 4-hydroxybenzoic acid and their monoanions were also obtained along with values of thermodynamic reaction quantities. The effects of water solvation and solvent polarization were accounted for by using both a polarizable continuum model (PCM) and a self-consistent isodensity polarizable continuum model (SCI-PCM). The calculated value of %@mt;sys@%Δ%@sb@%r%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@% for the conversion of chorismate^2-(aq) to {pyruvate^-(aq) + 4-hydroxybenzoate^-(aq)} at T = 298.l5 K was −154 kJ mol^-1 with the PCM model and −178 kJ mol^-1 with the SCI-PCM model. The relatively large discordance in the SCI-PCM calculation may arise from the ill-defined cavity size, which is derived from the solute charge distribution isosurface. However, the PCM model, which employs a parametrized cavity radius, yields a result that can be considered to be in agreement with experiment.

We examined the regulation of nitrogen metabolism in four classes (glnA, glnB, glnF, and glnG) of Gln- auxotrophs of Klebsiella pneumoniae. These studies indicate that glutamine synthetase does not directly mediate the physiological response to NH4+ in this organism. We present evidence suggesting that the effect of NH4+ on the expression of genes involved in nitrogen metabolism involves the products of the glnF and glnG genes.

We investigated the regulation of genes concerned with nitrogen metabolism by oxygen in the facultative anaerobe Klebsiella pneumoniae. We found oxygen to be required for the expression of the hut operons; the effect of O2 on the glutamine synthetase and urease was less pronounced than on the hut operons. Glutamine synthetase was transiently repressed during the transition from an aerobic to an anaerobic environment. Regulation of hut by O2 suppressed the effect of nitrogen limitation on the expression of these genes.

A thermodynamic investigation of the hydrolysis of sucrose to fructose and glucose has been performed using microcalorimetry and high-pressure liquid chromatography. The calorimetric measurements were carried out over the temperature range 298–316 K and in sodium acetate buffer (0.1 M, pH 5.65). Enthalpy and heat capacity changes were obtained for the hydrolysis of aqueous sucrose (process A): sucrose(aq) + H2O(liq) = glucose(aq) + fructose(aq). The determination of the equilibrium constant required the use of a thermochemical cycle calculation involving the following processes: (B) glucose 1-phosphate2−(aq) = glucose 6-phosphate2−(aq); (C) sucrose(aq) + HPO42−(aq) = glucose 1-phosphate2−(aq) + fructose(aq); and (D) glucose 6-phosphate2−(aq) + H2O(liq) = glucose(aq) + HPO42−(aq). The equilibrium constants determined at 298.15 K for processes B and C are 17.1 ± 1.0 and 32.4 ± 3.0, respectively. Equilibrium data for process D was obtained from the literature, and in conjunction with the data for processes B and C, used to calculate a value of the equilibrium constant for the hydrolysis of aqueous sucrose. Thus, for process A, ΔG0= −26.53 ± 0.30 kJ mol−1, K0= (4.44 ± 0.54) × 104, ΔH0= −14.93 ± 0.16 kJ mol−1, ΔSo= 38.9 ± 1.2 J mol−1K−1, and ΔCPo= 57 ± 14 J mol−1K−1at 298.15 K. Additional thermochemical cycles that bear upon the accuracy of these results are examined.

The thermodynamics of the hydrolysis of lactose to glucose and galactose have been investigated using both high pressure liquid chromatography and heat-conduction microcalorimetry. The reaction was carried out over the temperature range 282–316 K and in 0.1 Msodium acetate buffer at a pH of 5.65 using the enzyme β-galactosidase to catalyze the reaction. For the process lactose(aq) + H2O(liq) = glucose(aq) + galactose(aq), ΔG0= −8.72 ± 0.20 kJ·mol−1, K0= 34 ± 3, ΔH0= 0.44 ± 0.11 kJ·mol−1, ΔS0= 30.7 ± 0.8 J·mol−1·K−1, and ΔCpo= 9 ± 20 J·mol−1·K−1at 298.15 K. The standard state is the hypothetical ideal solution of unit molality. Thermochemical cycle calculations using enthalpies of combustion and solution, entropies, solubilities, activity coefficients, and apparent molar heat capacities have also been performed. These calculations indicate large discrepancies which are attributable primarily to errors in literature data on the enthalpies of combustion and/or third law entropies of the crystalline forms of the substrates.

Evidence is presented that monensin-sensitive membranes, presumably the Golgi apparatus, are involved in the synthesis of hyaluronate in rat fibrosarcoma cells. Monensin caused the inhibition of incorporation of metabolic precursors into hyaluronate produced by rat fibrosarcoma cells in a concentration- and time-dependent manner. Maximum inhibition (70-80%) was obtained on treatment with 10(-7) M monensin for 24 h. Incorporation of label into secreted hyaluronate and into that associated with the cell surface was inhibited, but incorporation into intracellular hyaluronate was not inhibited. In 3T3 cells, treatment for 24 h with 10(-7) M monensin inhibited incorporation of label only into secreted hyaluronate. The hyaluronate-rich pericellular coat, revealed by exclusion of fixed red blood cells, was depleted on treatment with monensin under the same conditions which caused inhibition of hyaluronate synthesis in the fibrosarcoma cells. Cell proliferation, as measured by DNA content/culture and [3H]thymidine incorporation, was also inhibited in a dose-dependent manner by monensin (10(-8)-10(-6) M). Protein synthesis was not inhibited at these doses, nor was monensin cytotoxic as judged by a 51Cr release assay. The inhibition of hyaluronate synthesis was independent of the antiproliferative effect of monensin because it was obtained during log phase growth or confluency and in the presence or in the absence of serum.

Presents `Video Review' magazine's 1992 buyer's guide to the audio equipment used in home theaters. Multichannel audio/video receivers; Dubbing capability; Dolby Pro Logic; Other features; List of audio/video receivers, sound processors, television tuners/multichannel television sound (MTS) decoders, and self-powered speakers; Denon AVC-3020 sound processor; Yamaha DSP-A100 sound processor; Sony SRS-67 self-powered speakers.

Presents a look at some of the latest home-video equipment. Philips' VR6065 VHS videocassette recorder; Sima's Pro Ed/it 3 video processing unit; Kenwood's LVD-700 laser disc player; Panasonic PV4164 VHS videocassette recorder; More.

Discusses the latest compact television monitor/receivers. Recent breakthroughs in cathode-ray tube and liquid crystal display technologies; How to choose a small-screen television that suits one's needs; Sony's `Watchman' pocket-sized LCD sets;Realistic's Pocketvision 24; Memorex's Portavision; Panasonic's 13-inch CTM-1355R; Magnavox's RS136OC; RCA Spacesaver ColorTrak; More. INSET: Batteries: The life of the party, by R.G..

Explains how to create computerized video images with a personal computer and home-video equipment. Explanation of terms such as genlock, grabbers, overlay, and others; Use of the Commodore Amiga, IBM Personal Computer, and the Apple MacIntosh with video add-ons; Format incompatibilities; NewTek's Video Toaster; Digital Vision's Computer Eyes; VideoLogic's DVA-4000; List of suppliers; More. INSET: A toast to video.;The marriage of computers and video..

Offers advice on converting a room into a home theater. Gives several examples. Room design; Audio/video equipment used; Planning; Airflow dilemma; How to work with an installer.

Lists the newest audio equipment for home theaters. Part of the `Video Review' Buyer's Guide 1991; A/V receivers; Sound processors; Television tuners and MTS decoders; Self-powered speakers; THX system, Dolby Surround, Digital Signal Processing (DSP) and other new features; Includes Carver, Pioneer, Technics, and others; Price range; Buying tactics.

Presents several state-of-the-art media rooms. Design philosophy; Integration of equipment and the total environment; Form and function; Comments by Kim Michels, President of Electronic Environments, a New York-based media room design firm. INSET: Credits..

Presents product evaluation results on eight big-screen television monitor/receivers tested by Advanced Product Evaluation Laboratory. Rear-projection monitors; Direct-view monitors; Mitsubishi 50-inch VS-5020R; NEC 52-inch DT-5271S; Sony 32-inchKV-32XBR70; More. INSET: Screening the sets (monitor calibration test signals), by L....

Examines the technology and aesthetics of creating a home theater sound system. Dolby Surround and competing technologies; Dolby Pro Logic; Shure's new Stereo Surround technology; Aphex Systems surround units built for Proton; Comments by spokesmen from companies competing with Dolby; How various systems work. INSET: From Disney to Dolby, by M. Wielage..

Names the winners of the first annual Great `Video Review' Shootoff home video movie competition. Grand prize winner `Contemporary Extemporary,' directed by Michael Dare of Los Angeles, Calif.; First and second prize winners in various categories; How winners were chosen. INSET: Honorable mentions (list of more home video movies, including....

1. The effects of daily administration of 50 or 100 mg of dl-ethionine on the rat pancreas is described.2. Degenerative changes in the acinar tissue occurred as early as 12 hours after a single injection of 50 mg dl-ethionine.3. Daily injections of 50 or 100 mg in non-fasted rats, for 2 weeks, resulted in almost complete obliteration of the acinar tissue accompanied by fibrous proliferation.4. No histological evidence of islet damage was observed with these dosages.

Examination of 10 rats sacrificed 18 months after a single injection of 400 μc of radioactive iodine revealed the following changes in the thyroid gland: 1. Hürthle-like elements (previously reported by us in thyroids of rats sacrificed 8 months after a single I131injection) were evident in the parenchyma of all glands. 2. Multiple adenomata, apparently benign in nature, were found in the thyroids of 2 rats. 3. Two types of anaplastic, nonencapsulated neoplasms, one of which was invading adjacent thyroid tissue, were also found in the thyroids of these 2 rats.

An inhibition of HSV DNA synthesis was observed in infected RK cells following treatment with the carcinogenic polycyclic aromatic hydrocarbon, DMBA. No such effect was observed in replicate cultures treated with the related but noncarcinogenic chemical, anthracene. The compounds were without cytocidal effects in the experimental system employed at the concentrations tested.This investigation was supported in part by Public Health Service Research Grant No. CA-11647 from the National Cancer Institute and under Contract No. 70-2024 within the Special Virus Cancer Program of the National Cancer Institute, National Institutes of Health, U.S. Public Health Service.

A classification of retrobulbar A-mode echogram patterns is described following examination of 60 patients with unilateral proptosis. Sixty percent of 20 verified orbital neoplasms revealed one of the following axial length differences, dampening of retrobulbar echoes and tumor-cyst patterns. Five of eight undetected neoplasms were confined to the orbital apex. All patients with endocrine exophthalmos (ten) and orbital cellulitis (six) had normal echograms. Pseudoproptosis (ie, unilateral high-axial myopia or unilateral glaucoma) was easily detected due to increased ultrasonic axial measurements (five). Time-amplitude (A-mode) ultrasonography is unidirectional. All ultrasonic interpretations are subjectively made by the physician by comparing the acoustical properties of both orbits. Although this method cannot outline retrobulbar masses two-dimensionally as with intensity-modulation techniques, the ability to detect orbital neoplasms and exclude all instances of pseudoproptosis makes this technique clinically valuable and worth further clinical testing and refinement.

Maintenance of hypophysecto-mized rats on a diet deficient in iodine resulted in 1) an apparent increase in the efficiency of iodine extraction from the blood by the thyroid gland; 2) no reduction in thyroid gland iodine content and, 3) a slight and questionably significant increase in thyroid acinar cell height accompanied by other morphological manifestations of increased activity. It is suggested that hypophyseal thyrotropin is not the only factor capable of stimulating the thyroid gland.

Pars distalis-extract treatment of intact or ‘hypophysectomized’ chicken embryos resulted in a splenomegaly, perhaps of a host-versus-graft nature, by 17 and 17·5 days of incubation. Pars distalis grafts in intact embryos reduced spleen size, encouraged white-pulp follicle formation, but ‘suppressed’ red-pulp development. Adult spleen extract and bovine serum albumin did not change spleen sizes or histology appreciably in intact embryos. Perhaps pars distalis hormones inhibit red-pulp development or stimulate white-pulp follicles which may compete with red-pulp proliferation but encourage splenic vasculogenesis alone or by stimulating adrenocorticoid, thyroid, and other hormone levels while other extract factors cause splenomegaly.

A personal narrative is presented in which author share his experience on lonely grave with no signs of habitation and self-determination of nations and speech from U.S. former President Thomas Woodrow Wilson at Peace Conference.

The patient in status epilepticus presents many challenges to the emergency physician. IV access is frequently difficult to achieve, and prolonged attempts at access can jeopardize the patient and endanger the caregiver. We present two cases in which the administration of intranasal midazolam appeared to successfully terminate status epilepticus. No adverse effects were noted. Studies are needed to clarify the safety, optimal dosing, and clinical utility of this treatment modality. [Kendall JL, Reynolds M, Goldberg R: Intranasal midazolam in status epilepticus. Ann Emerg Med March 1997;29:415-417.]

The photoresponse of Schottky and np-diamond diodes has been measured from 120 to 600 nm. The ultraviolet response is 100 times the visible response.

The viomycin phosphotransferase gene (vph) is expressed and confers resistance to viomycin in both Streptomyces spp. and members of the family Enterobacteriaceae. We report the isolation of UGA (opal) and UAG (amber) mutations in the vph gene of shuttle plasmid pVE138. We found that the five UGA mutations in vph resulted in a temperature-sensitive phenotype in Salmonella typhimurium. Su- strains are Vior at 28 degrees C and Vios at 37 degrees C, whereas Su+UGA strains are Vior at both 28 and 37 degrees C. The single amber mutation isolated was not temperature sensitive and resulted in the expected Vios phenotype in Su- strains and Vior in Su+UAG strains.