Maximum axial root growth pressure in pea seedlings: effects of measurement techniques and cultivars

Values of the maximum axial growth pressure (σ_max) of seedling pea (Pisum sativum L.) roots reported in the literature, obtained using different apparatuses and cultivars, range from 0.3 MPa to 1.3 MPa. To investigate possible reasons for this large range, we studied the effect of apparatus and cultivar on measurements of σ_max in peas. We describe four types of apparatus which can be used to measure axial root growth force and hence σ_max, and used them to measure σ_max in seedling pea roots using cultivar Meteor. Two of these apparatuses were also used to compare σ_max for three pea cultivars (Helka, Meteor and Greenfeast). Both cultivar and apparatus significantly affected σ_max , but there were greater differences between apparatuses than between the three cultivars. Estimating root cross-sectional area from the diameter of cross-sections, rather than from in situ measurements (i.e. measurements made with the root still in place in the apparatus) may explain these differences. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synchronous intra-Golgi transport induces the release of Ca from the Golgi apparatus

The mechanisms of secretory transport through the Golgi apparatus remain an issue of debate. The precise functional importance of calcium ions (Ca²⁺) for intra-Golgi transport has also been poorly studied. Here, using different approaches to measure free Ca²⁺ concentrations in the cell cytosol ([Ca²⁺]_cyt) and inside the lumen of the Golgi apparatus ([Ca²⁺]_GA), we have revealed transient increases in [Ca²⁺]_cyt during the late phase of intra-Golgi transport that are concomitant with a decline in the maximal [Ca²⁺]_GA restoration ability. Thus, this redistribution of Ca²⁺ from the Golgi apparatus into the cytosol during the movement of cargo through the Golgi apparatus appears to have a role in intra-Golgi transport, and mainly in the late Ca²⁺-dependent phase of SNARE-regulated fusion of Golgi compartments.     

Aquatic insect larvae as indicators of limiting minimal contents of dissolved oxygen

Minimal concentrations of oxygen are limiting factors for limnic biocenoses. It should therefore be possible to use biocenose structure to infer minimal oxygen concentrations that have occured, provided the tolerance of the organisms concerned is known. A simple apparatus used to measure LC₅₀ of oxygen for aquatic insect larvae with tracheal gills is described. Lethal concentrations found in some Ephemeroptera differ between species. Usually, they are strongly temperature dependent. In the species so far studied, confidence intervals are very small and suggest that such insect larvae could be used as bioindicators of minimal oxygen concentrations (even of short term ones), especially in thermically stable waters.     

An Apparatus for Concentrating Dilute Protein Solution by Perosmosis Against Polyethylene Glycol

An apparatus is described for the continuous concentration of dilute protein solutions by perosmosis. In this apparatus polyethylene glycol of average molecular weight 20, 000, fractionated with (NH₄)₂SO₄ to eliminate the lower molecular weight entities, is used.     

RECONSTRUCTION OF AN APPARATUS OF NEOSTRACHANOGNATHUS TAHOENSIS FROM ORITATE,JAPAN AND SPECIES OF NEOSTRACHANOGNATHUS FROM OMAN

Abstract: The apparatus of an Early Triassic conodont Neostrachanognathus tahoensis Koike, 1998 from Oritate, Kumamoto Prefecture, Japan, and a species of Neostrachanognathus from Oman were reconstructed. On the basis of five natural assemblages from the Oritate area, the three‐dimensional apparatus model of N. tahoensis is interpreted as bilaterally symmetrical and composed of 14 elements consisting of pairs of P₁, P₂, P₃, S₁, S₂, S₃, and S₄ elements. The P₁ and P₂ elements are coniform elements, the P₃ elements are digyrate forms, and the S elements are bipennate ramiforms. The S elements are arranged rostrally in the apparatus and the pairs of the P₁, P₂, and P₃ elements are subvertically arranged caudally and ventrally to the S array. One of the natural assemblages was formed by rostrocaudal collapse of the apparatus on the sea floor, whereas the other assemblages indicate that conodont animals came to rest nearly parallel with the substrate prior to burial. A collection of isolated elements from Jabal Safra, Oman, includes a second species of Neostrachanognathus with a comparable apparatus.     

Measurement of Ensemble TRPV1 Ion Channel Currents Using Droplet Bilayers

Electrophysiological characterization of ion channels is useful for elucidation of channel function as well as quantitative assessment of pharmaceutical effects on ion channel conductance. We used droplet bilayers to measure ensemble ion channel currents from membrane preparations made from TRPV1-expressing HEK cells. Conductance measurements showed rectification, activation by acid and capsaicin, and inhibition by capsazepine, SB 452533, and JNJ 17293212. We also quantitatively measured concentration-dependent inhibition of channel conductance through determination of capsazepine IC₅₀ in agreement with previously published studies using patch clamp. These results, combined with the reduced apparatus and material requirements of droplet bilayers, indicate that this platform could be used for study of other physiologically relevant ion channels.     

Laboratory-Produced CO(2) Calibration Gases

A simple, inexpensive apparatus for making mixtures of accurately known amounts of CO₂ and CO₂-free atmospheric air is described. Calibration gases with CO₂ contents of 200 to 1500 microliters per liter produced with the apparatus had concentrations which were within 10 microliters per liter of the target concentration.     

A rapid sampling method for measuring efflux from erythrocytes.

A method is described for obtaining kinetic data using a water-jacketed Hamilton gas-tight syringe as a reaction vessel and delivering aliquots of the reaction mixture to a quench solution at intervals as small as 2 sec apart by means of a repeating dispenser attachment. This apparatus has been used to measure the rate of [¹⁴C]uridine equilibrium exchange efflux from human erythrocytes at 15°C and at uridine concentrations near the K_m for the transport process. It should be useful for kinetic studies of any reaction having a half time of the order of 4 sec or more, provided a method of rapidly quenching the reaction is available.     

Influence of age of mycelium and water activity of the medium on aroma production by Trichoderma viride grown on solid substrate

The production of 2-heptanone (cheese aroma) by Trichoderma viride TS cultivated on agar media was evaluated using headspace gas chromatographic analysis. The radial growth rate of the filamentous fungi increased with high water activity values, but the mycelial density was higher for lower water activity. Maximum aroma production of a culture was obtained at a_w = 0.96. An apparatus intended to measure the aroma production of different areas of a mycelial colony was set up. The study of the aroma production of these areas showed that the production values were greatly different and were evolving with time. It was shown that the mycelium aroma production was maximum when mycelia were about 3.5 to 6.5 d old.     

Method for Simultaneous Measurement of Radioactive and Inactive CO(2) Evolved from Soil Samples During Incubation with Labeled Substrates

An apparatus is described which allows the simultaneous, continuous, and highly sensitive analysis of inactive and radioactive CO₂ evolved from ¹⁴C-supplemented soils or other materials. The apparatus consists of a control unit, a commercially available conductometric CO₂ analyzer, and fraction collector. A number of model experiments were conducted to demonstrate the potentials of the apparatus. These included analysis of the time course of priming action, when ¹⁴C-glucose was added to soil, separation of CO₂ respiration peaks caused by simultaneous degradation of radioactive and inactive soil supplements, and study of the effects of a fungicide, Benomyl, on degradation of ¹⁴C-labeled glucose. In the last experiment, partial degradation of the fungicide could also be followed.     

Method for Simultaneous Measurement of Radioactive and Inactive CO2 Evolved from Soil Samples During Incubation with Labeled Substrates

An apparatus is described which allows the simultaneous, continuous, and highly sensitive analysis of inactive and radioactive CO₂ evolved from ¹⁴C-supplemented soils or other materials. The apparatus consists of a control unit, a commercially available conductometric CO₂ analyzer, and fraction collector. A number of model experiments were conducted to demonstrate the potentials of the apparatus. These included analysis of the time course of priming action, when ¹⁴C-glucose was added to soil, separation of CO₂ respiration peaks caused by simultaneous degradation of radioactive and inactive soil supplements, and study of the effects of a fungicide, Benomyl, on degradation of ¹⁴C-labeled glucose. In the last experiment, partial degradation of the fungicide could also be followed.     

Evidence that UV-B tolerance of the photosynthetic apparatus in microalgae is related to the D1-turnover mediated repair cycle in vivo

The present study was conceived to elucidate the potential importance of the D1 turnover-mediated repair mechanism in UV-B tolerance of the photosynthetic apparatus in microalgae. To this end, the lab-identified UV-B sensitive and tolerant species of Chlorophyte and Chromophyte algae was used to examine photosynthetic response to UV-B exposure in the presence vs. the absence of streptomycin, an inhibitor of chloroplast protein synthesis. Measurements of photosynthetic O₂ evolution capacity and chlorophyll fluorescence parameters (F_v/F_m, Φ_PSII) illustrated species-specific UV-B sensitivity of the photosynthetic apparatus. Addition of the inhibitor streptomycin caused significant enhancements of UV-B-caused depression of photosynthesis in UV-B tolerant species, while little effect was observed in the sensitive species. In the tolerant species, recovery from UV-B induced 20 percnt; decline in F_v/F_m reached completion within 2 hours, much faster than that in the sensitive species. Immunoblotting revealed that exposure to UV-B radiation caused substantial degradation of the D1 protein in the sensitive Heterococcus brevicellularis, which was little enhanced by addition of the inhibitor. The same UV-B exposure lead to less D1 degradation in the tolerant Scenedesmus sp., which was significantly enhanced by addition of the inhibitor. This study shows that UV-B tolerance of the photosynthetic apparatus in microalgae was associated with a strong capacity for recovery from the UV-B-induced damage and this capacity related to the D1 turnover-mediated repair cycle, and largely determined UV-B tolerance of the photosynthetic apparatus in these organisms.     

Purification of a UTP: d-Glucose-1-phosphate uridylyl-transferase from Golgi apparatus of cat liver by affinity chromatography on UTP-agarose

UDP-glucose pyrophosphorylase from Golgi apparatus solubilized by detergent has been purified 100-fold from microsomes by affinity chromatography on UTP-agarose. The purified enzyme has apparent M_r 270,000 and isoelectric pH 3.9 against 360,000 and 4.2 for soluble enzyme. According to these characteristics, UDP-glucose pyrophosphorylase from Golgi apparatus is different from cytosolic enzyme.     

Cadmium toxicity affects photosynthesis and plant growth at different levels

In this article we discuss and update some of the effects of Cd toxicity on the photosynthetic apparatus in a model crop Lactuca sativa. Seeds of L. sativa were germinated in solutions with 0, 1, 10 and 50 μM of Cd(NO₃)₂ and then transferred to a hydroponic culture medium. After 28 days, the effects of Cd on the photosynthetic apparatus of lettuce were analysed. Exposure of lettuce to 1 μM Cd(NO₃)₂ affected already plant growth (dry biomass), but, did not induce serious damages in the photosynthetic apparatus. However, increasing concentrations of this metal to 10 and 50 μM promoted a strong reduction of the maximum photochemical efficiency of PSII and an impairment of net CO₂ assimilation rate, putatively due to Rubisco activity decrease. This ultimately results in a strong inhibition of plant growth. Nutrient uptake and carbohydrate assimilation were also severely affected by Cd.     

Simultaneous measurement of oxygen evolution and chlorophyll fluorescence from leaf pieces

An apparatus is described which permits the simultaneous measurement of O₂ evolution and chlorophyll a fluorescence from illuminated discs or pieces of green leaves. O₂ is measured in the gas phase in a temperature-controlled chamber of approximately 5-milliliter capacity. Calibration is effected by injection of air through vents. Response time is approximately 1.5 seconds for O₂, and full scale deflection, in normal operating mode, is approximately 10 micromoles O₂. The apparatus may also be used to monitor fluorescence alone, in an open mode, in which gas is passed continuously through the chamber.     

Response of the Photosynthetic Apparatus of the Diatom Thallassiosira weisflogii to High Irradiance Light

The response of the photosynthetic apparatus to high irradiance illumination (440–2200 W/m²) was studied in the diatom Thallassiosira weisflogii by fluorescence methods. Changes in the photosynthetic apparatus were monitored by measuring characteristics of chlorophyll fluorescence F ₀, F _m, F _v/F _m, and qN for several hours after illumination of the alga with high-intensity light. Incubation of the alga with 2 mM DTT, an inhibitor of de-epoxidase of carotenoids in the diadinoxanthin cycle, led to a decrease in the nonphotochemical quenching of chlorophyll fluorescence and a drop in the F _v/F _m ratio, a characteristic that reflects the quantum efficiency of the functioning of the photosynthetic apparatus. Light-induced absorption changes associated with transformations of carotenoids of diadinoxanthin cycle were recorded in vivo in algal suspensions in the absence and in the presence of DTT. Using the microfluorometric method, we measured cell distribution over the efficiency of the primary processes of photosynthesis (F _v/F _m) after illumination. We found cells with a high tolerance of their photosynthetic apparatus to photooxidative damage. The relatively high tolerance of a portion of the cell population to high-light illumination can be related to light-induced transformation of carotenoids and to the functioning of other protective systems of the photosynthetic apparatus in diatoms.     

A simple apparatus for the continuous monitoring of 14CO2 production from several small reaction mixtures

A simple apparatus is described which permits the continuous monitoring of ¹⁴CO₂ production from ten separate reaction mixtures simultaneously. The device is relatively simple and inexpensive to construct, makes use of small disposable incubation vials, and allows complete trapping of all ¹⁴CO₂ evolved in scintillation vials, where it can be easily counted. The use of this apparatus to determine the rates of metabolism by glomeruli of ¹⁴C-labeled substrates to ¹⁴CO₂ is described.     

Working design for a 5-liter controlled continuous culture apparatus

A continuous culture apparatus of 5-liter capacity is described which is capable of control of dissolved oxygen. Combined turbidostat and constant feed operation permit control of cell population density and one or more nutrients. A system for the measurement of oxygen uptake and CO₂ output is described. Sufficient detail is supplied to enable construction and operation of the apparatus.     

Development of an apparatus for cultivation of anaerobic microorganisms

Summary A novel apparatus with an L-shaped test tube was developed for anaerobic cell cultivation. Anaerobic condition was achieved without the rigorous gassing with CO₂ during the various stages of medium preparation. dispensation and cell inoculation. The growth of both moderate and strict anaerobes in this apparatus were similar to those obtained with the glove box method.     

Weak Interactions between Salmonella enterica FlhB and Other Flagellar Export Apparatus Proteins Govern Type III Secretion Dynamics

The bacterial flagellum contains its own type III secretion apparatus that coordinates protein export with assembly at the distal end. While many interactions among export apparatus proteins have been reported, few have been examined with respect to the differential affinities and dynamic relationships that must govern the mechanism of export. FlhB, an integral membrane protein, plays critical roles in both export and the substrate specificity switching that occurs upon hook completion. Reported herein is the quantitative characterization of interactions between the cytoplasmic domain of FlhB (FlhB_C) and other export apparatus proteins including FliK, FlhA_C and FliI. FliK and FlhA_C bound with micromolar affinity. K_D for FliI binding in the absence of ATP was 84 nM. ATP-induced oligomerization of FliI induced kinetic changes, stimulating fast-on, fast-off binding and lowering affinity. Full length FlhB purified under solubilizing, nondenaturing conditions formed a stable dimer via its transmembrane domain and stably bound FliH. Together, the present results support the previously hypothesized central role of FlhB and elucidate the dynamics of protein-protein interactions in type III secretion.