Integrated temporal regulation of the photorespiratory pathway. Circadian regulation of two Arabidopsis genes encoding serine hydroxymethyltransferase.

The photorespiratory pathway is comprised of enzymes localized within three distinct cellular compartments: chloroplasts, peroxisomes, and mitochondria. Photorespiratory enzymes are encoded by nuclear genes, translated in the cytosol, and targeted into these distinct subcellular compartments. One likely means by which to regulate the expression of the genes encoding photorespiratory enzymes is coordinated temporal control. We have previously shown in Arabidopsis that a circadian clock regulates the expression of the nuclear genes encoding both chloroplastic (Rubisco small subunit and Rubisco activase) and peroxisomal (catalase) components of the photorespiratory pathway. To determine whether a circadian clock also regulates the expression of genes encoding mitochondrial components of the photorespiratory pathway, we characterized a family of Arabidopsis serine hydroxymethyltransferase (SHM) genes. We examined mRNA accumulation for two of these family members, including one probable photorespiratory gene (SHM1) and a second gene expressed maximally in roots (SHM4), and show that both exhibit circadian oscillations in mRNA abundance that are in phase with those described for other photorespiratory genes. In addition, we show that SHM1 mRNA accumulates in light-grown seedlings, although this response is probably an indirect consequence of the induction of photosynthesis and photorespiration by illumination.

Clinical features of inflammatory liver disease in cats: 41 cases (1983-1993).

OBJECTIVE: To compare the clinical and clinicopathologic findings in and prognosis for cats with lymphocytic portal hepatitis (LPH) versus cats with acute or chronic cholangiohepatitis (CH). DESIGN: Retrospective study. ANIMALS: 25 cats with LPH; 16 cats with CH (7 acute, 9 chronic). PROCEDURE: Cats with LPH and CH were selected by evaluating records from liver biopsy specimens submitted to the University of Minnesota Veterinary Teaching Hospital during a 10-year period. Clinical and clinicopathologic data were retrieved. RESULTS: Cats with CH had higher segmented and band neutrophil counts, alanine aminotransferase activities, and total bilirubin concentrations than did cats with LPH. Cats with acute CH had higher segmented and band neutrophil counts and lower serum alkaline phosphatase activities and total bilirubin concentrations than did cats with chronic CH. Twelve of 14 cats with LPH or CH had coarse or nodular texture to the liver on ultrasonography, with loss of portal vein wall clarity noticed in 4 of 8 cats with LPH. Sixteen of 23 cats with LPH and 8 of 15 cats with CH survived > 1 year. Of those cats living < 1 year, all cats with LPH and 5 of 7 cats with CH had a serious concurrent illness that may have been responsible for their deaths. CLINICAL IMPLICATIONS: LPH and CH can be detected and tentatively differentiated through evaluation of clinical laboratory test results, but histologic evaluation of liver specimens is necessary for definitive differentiation. Survival time was good regardless of the type of inflammatory liver disease.

Relationship between inflammatory hepatic disease and inflammatory bowel disease, pancreatitis, and nephritis in cats.

OBJECTIVE: To determine whether cats with inflammatory hepatic disease had concurrent inflammatory bowel disease (IBD), pancreatitis, or chronic interstitial nephritis. DESIGN: Prospective case series. SAMPLE POPULATION: 78 tissue sections of liver, intestine, pancreas, and kidney from cats that had previous necropsy examinations at the teaching hospital. PROCEDURE: We reviewed histologic sections of liver, intestine, pancreas, and kidney from cats that had previous necropsy examinations and determined the prevalence of lymphocytic portal hepatitis, cholangiohepatitis, IBD, pancreatitis, and chronic interstitial nephritis, and the relationship among them. RESULTS: 36 cats had lymphocytic portal hepatitis, 18 had cholangiohepatitis, and 24 did not have inflammatory hepatic disease. The prevalence of IBD (10/36; 28%) and pancreatitis (5/36; 14%) in cats with lymphocytic portal hepatitis was not significantly different from cats without inflammatory hepatic disease. The prevalence of IBD (15/18; 83%) and pancreatitis (9/18; 50%) was greater (P < 0.05) for cats with cholangiohepatitis, compared with cats without inflammatory hepatic disease. Thirty-nine percent of cats (7/18) with cholangiohepatitis had IBD and pancreatitis. Evidence of IBD in association with cholangiohepatitis was characterized by infiltration of lymphocytes and plasma cells into the lamina propria; however, neutrophilic infiltrates also were found in 6 of 15 (40%) cats with cholangiohepatitis. Pancreatitis was mild in all cats. CLINICAL IMPLICATIONS: Cats with a diagnosis of cholangiohepatitis should be evaluated for IBD and pancreatitis.

Histopathologic evaluation of feline inflammatory liver disease.

To better define the histopathologic features of feline inflammatory liver disease, we studied feline liver biopsies evaluated at the University of Minnesota Veterinary Teaching Hospital over a 10-year period. Of 175 liver sections examined, 45 had portal inflammatory infiltrates. Of these, 60% had infiltrates consisting of lymphocytes and plasma cells, 24% had infiltrates consisting of neutrophils, and 16% had mixed infiltrates consisting of neutrophils, lymphocytes, and plasma cells. Lymphocytic-plasmacytic portal infiltrates were characterized by various degrees of bile duct proliferation and fibrosis without evidence of bile duct infiltration or periportal necrosis. Sections with portal neutrophilic infiltrates were characterized by bile duct infiltration, bile duct epithelial degeneration, periportal necrosis, and infiltration of neutrophils into adjacent lobules. We propose that hepatitis characterized by portal lymphocyte and plasma cell infiltration be termed lymphocytic portal hepatitis and that hepatitis characterized by cholangitis and portal neutrophilic infiltrates with or without lymphocytes and plasma cells be termed cholangiohepatitis.

Characterization of portal lymphocytic infiltrates in feline liver.

To better understand the relationship of portal lymphocytic infiltrates to feline inflammatory liver disease, liver sections were semiquantitatively evaluated from healthy cat and liver sections randomly selected at necropsy from clinical cases. Healthy specific pathogen-free kittens and healthy young adult cats had up to 10 lymphocytes and plasma cells per portal area. Neutrophils were infrequently seen in portal areas. Approximately one-third of sections obtained from clinical cases younger than 10 years had increased numbers of lymphocytes and plasma cells in portal areas. Seventy percent of these had a concurrent increase in neutrophils. Eighty-two percent of liver sections obtained from clinical cases older than 10 years had increased numbers of portal lymphocytes and plasma cells. Almost all of these sections had concurrent fibrosis and bile duct proliferation. These data indicate that a progressive lymphocytic portal hepatitis is a common finding in cats older than 10 years.

Frequency locking of laser diode using metallic vapor optogalvanic spectrum: Ui.

The frequency of a AlGaAs diode laser has been locked to the 8118-cm(-1)(f(3)d(2)s(5)M(0)(7))-20,218-cm(-1) transition of UI at 826.20570 nm using the optogalvanic effect. A hollow cathode vapor generator has been utilized to produce a density of 10(12) atoms/cm(3) of uranium in vapor phase. The absolute frequency stability for a 10-min run was estimated to be better than 500 kHz P-P at an integration time of 1 s. This preliminary result shows that the rich optogalvanic spectrum of uranium can be efficiently used for the frequency-locking of semiconductor lasers.

Atom confinement in a laser open atomizer.

We have investigated the effects of a buffer gas (air) on the vapor plume produced in a laser open atomizer using atomic absorption spectroscopy. The absorption signal is related to the concentration of absorbing species by a modified Beer-Lambert equation in which the buffer gas pressure and temperature and the diameter of the diffusing species appear explicitly. Our experimental results show that the observed maximum of absoprtion as a function of gas pressure is well explained by the classical gas diffusion theory. Furthermore, our measurements indicate that the plume created by the laser has a conical shape.

Simple method for identifying doubly ionized uranium (U III) produced in a hollow-cathode discharge.

We have studied by emission spectroscopy the spectral properties of doubly ionized uranium, produced in a vapor generator of hollow-cathode design, as a function of the nature of a pure fill gas (helium, neon, argon, krypton, xenon) and its pressure. The spectral intensity is found to increase with increasing ionization potential of the discharge buffer gas, except in the case of helium. Based on our preliminary results, a simple and practical method for the positive identification of the complex U III spectrum is suggested.

Ultraviolet optogalvanic laser spectroscopy of iron for reference wavelengths.

We present a preliminary study of a UV optogalvanic spectrum obtained by using a see-through iron hollow cathode and a tunable pulsed laser in the 240-260-nm range. The hollow cathode used and described is a homemade device that can be run in static- or dynamic-flow gas regimes. Spectra have been recorded with argon and neon buffer gases, and many classified Fe I lines have been identified. The accuracy of the measured wave numbers is limited at present to 0.05 cm(-1) by the spectral width of the UV laser. This iron optogalvanic spectrum is proposed for reference-wavelength calibration in UV laser spectroscopy, and an application to the study of Ba(+) Rydberg levels is reported. Possibilities for future developments of such a device are analyzed.

Ionization and excitation of uranium in a hollow-cathode lamp.

The influence of different carrier gases (Ne, Ar, Kr, Xe), their pressure, and discharge current on the excitation and ionization of uranium atoms in a vapor generator of hollow-cathode design has been investigated by monitoring emission line intensities. From our measurements of line intensities as a function of the carrier gas we obtain an indication of the role of Penning collisions on the excitation of radiative levels in U II.

Déformations du profil du coefficient d'absorption de la raie 5915 A UI dans un générateur de vapeur à cathode creuse pulsée.

During the development and study of a hollow cathode pulsed source of uranium vapor, we have observed that the absorption line shape changes considerably with time. This has been shown to be due to oscillatory collective displacement of the vapor in the cavity of the source.

Utilisation d'une ligne de microphotodiodes en spectrographie Fabry-Perot.

A self-scanned photodiode array has been used to detect the image from a Fabry-Perot spectrograph, the recording being a cut along a diameter of the interference pattern. A microcomputer plus a 12-bit analogto- digital converter are employed to store numerically the data as a central logic system and to eliminate the fixed pattern noise of the array. From the spatial photosensibility distribution, we can restore the profile of the light distribution at the sampled points. Using the Shannon interpolation method on these ideal samples, we can thus pinpoint precisely the maxima of the fringes and linearize the spectra. Theoretical and experimental comparisons with photographic plates pointed out an improvement in the SNR for the photodiode system and open up interesting and useful applications to Fabry-Perot spectrography.

Design of a compact cw chemical HF/DF laser using a microwave discharge.

A compact cw chemical HF/DF laser is described. The laser system consists of a microwave discharge using a surfatron to dissociate SF6 molecules mixed with He, a reaction chamber engineered to provide a fast mixing of reacting atoms and molecules, and an optical resonator which includes a concave mirror and a blazed grating for line selection, both mounted on a rigid Invar frame. The laser oscillates on a single line single TEM00 mode over many P transitions of HF and DF with a typical intensity fluctuation of 5% and a frequency jitter of about 30 MHz.

Etude par absorption d'un faisceau laser d' une vapeur d' (238)U ((5)L(0)(6)) obtenue à l' aide d'une lampe à cathode creuse.

The density of U atoms in the (5)L(0)(6) ground state present in a vapor of this element from a hollow cathode lamp has been measured using laser absorption spectroscopy. The influence of the carrier gases (Ar, Kr, Xe) on the density, the absorption coefficient profiles, and on the ratio of U atoms to the dissipated electrical power has been investigated. It has been found that, in our range of operating conditions, the xenon gas is the most efficient. With xenon, a density of 2.2 x 10(12) cm(-3) ground-state U atoms is obtained when the lamp dissipates 40 W of electrical power.

Générateur de vapeur d'uranium: la lampe à cathode creuse pulsée.

The production of uranium vapors has been studied in the (5)L(0)(6)ground state using a pulsed hollow cathode lamp. The evolution of the (238)U ((5)L(0)(6)) concentration with time has been studied with Xe and Ar as buffer gases. A density of 2.7 x 10(13) atoms cm(-3) was obtained with Xe as a buffer gas. In addition, those measurements, obtained from the absorption of a laser beam tuned to the 5758.143 A ((5)L(0)(6)-17,361(7)L(6)) transition, allowed the determination of the transition probability A = 2.1 x 10(5) sec(-1) and of the branching ratio BR = 0.08 for this transition.