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1.
Summary Four isolates ofCytospora cincta
Fr. and 2 ofC. leucostoma
Fr. were cultured on media containing 7 different nitrogenous compounds. Maltose served as a constant source of carbon. All experiments were carried out at 25° C.Total growth as determined by mycelial weights, and degree of sporulation as determined by an arbitrary system, revealed that 1) potassium nitrate was most satisfactory as a source of nitrogen, 2) response of the isolates tended to segregate them along species lines, and 3) the pH of the medium appeared to be a factor in the degree of response.Growth-habit experiments emphasized 1) extreme variation in colony characteristics and 2) the need for standardization of laboratory environments for comparative studies of the fungi.Approved by the Director of the Idaho Agricultural Experiment Station as Research Paper No. 518. 相似文献
2.
An optimum environment for the culturing of cytospora isolates from stone fruits. II. Carbon sources
Summary Six isolates (Cytospora cincta
Fr. andC. leucostoma
Fr.) were innoculated to liquid and solid synthetic laboratory media containing nine different sources of carbon.One of the isolates did not grow. The remaining five grew at rates, and in relationships, which segregated them in accordance with their species grouping. These relationships were more nearly constant than any other relationships previously noted in Idaho for these or otherCytopora isolates.Two conclusions were reached: 1) For best growth and sporulation, maltose should be incorporated in the laboratory culture medium and not the commonly used dextrose, which was demonstrated to be an inferior source of carbon; and 2) separate investigations, which utilize different carbon sources in the laboratory media, are likely to yield sufficiently different results that co-identity of species strains used by the separate workers may not be evident.Approved by the Director of the Idaho Agricultural Experiment Station as Research Paper No. 489. 相似文献
3.
Summary Four isolates ofCytospora cincta
Fr. and 2 ofC. leucostoma
Fr. were obtained from diseased Italian prune, President plum and Bing cherry trees.The minimum temperature for growth of these fungi was found to be 3° C. Temperatures of 45 °C. were lethal to all cultures. The optimum temperature for theC. cincta isolates on solid and liquid media was found to be 30° C.; for theC. leucostoma isolates, nearly 25° C. OneC. cincta isolate produced greatest radial growth on the solid medium at 35° C., but in the liquid medium produced maximum mycelium at 30° C.All factors considered, the conclusion was reached that the best single temperature for laboratory culture of the fungi was 30° C.Approved by the Director of the Idaho Agricultural Experiment Station as Research Paper No. 493. 相似文献
4.
Summary Storage protein bodies from sunflower cotyledons during early stages of seed germination were isolated on sucrose density gradients by isopycnic centrifugation. The density of this organelle on the gradients ranged between 1.26 and 1.36 g cm-3. A proteinase with a pH optimum of 5.2 was associated with this organelle, and is probably responsible for degradation of storage protein. A NADH-dependent cytochrome-c reductase, a membrane marker enzyme with a pH optimum of 8.4, was also present in this organelle fraction.Abbreviations LPA
for l-lysine-p-nitroanilide
- LPAase
for the peptidase which hydrolyzes this peptide
This work was supported in part by the National Science Foundation Grant GB-17543, and published as Journal Article No. 5736 of the Michigan Agricultural Experiment Station.Supported by a Deutsche Forschungsgemeinschaft Fellowship. 相似文献
5.
Mary K. Johnson 《Antonie van Leeuwenhoek》1973,39(1):599-608
Some properties of a purified peptidase fromDiplococcus pneumoniae have been studied. The enzyme has a broad pH optimum between 6 and 8 and a Km (onl-leucylglycylglycine) of 2.8mm. It is activated by low levels of Hg++ and is inhibited by Mn++, Co++, β-mercaptoethanol and EDTA. Substrate specificity studies show that the enzyme is an exopeptidase of the aminopeptidase
type, most active on tripeptide substrates bearing bulky substituents at the NH2
− terminal end. 相似文献
6.
Summary NADH oxidation with the particulate fraction from dark aerobically grown Rhodospirillum rubrum is significantly stimulated by the addition of phosphate (Pi) and Mg++, or Pi, Mg++, ATP and the hexokinase-glucose system. K
m
values for Pi in NADH oxidation and phosphorylation are 10–3
m and 8×10–4
m, respectively. These K
m
values are almost the same as in corresponding photophosphorylation and oxidative phosphorylation catalyzed with chromatophores. As in the case of NADH oxidation with chromatophores, NADH oxidation with the particulate fraction has an optimal pH at 7.5 without additions, which is shifted to 6.9 by the addition of Pi and Mg++, or Pi, Mg++, ATP and the hexokinase-glucose system. The optimal pH for coupled phosphorylation is 6.9. 10 g per ml of oligomycin can suppress stimulation of NADH oxidation by Pi, or by the energy trapping system, and prevent the shift of optimal pH. The particulate fraction can catalyze Pi-incorporation into glucose-6-phosphate without externally added ATP, so that Pi-incorporation is inhibited by oligomycin. From these findings, it is concluded that NADH oxidation in the particulate fraction is tightly coupled to phosphorylation. 相似文献
7.
Soil additions of Cl–, as NaCl, over the 0 to 400 ppm Cl– range did not affect germination forAndropogon scoparius. Height and top dry weight were significantly reduced by 300 ppm soil added Cl–. Although not conclusive, these results did indicate that growth and germination effects reported for Cd++, added as CdCl2, are probably due to Cd++ rather than to a Cl– or salt effect. Reported Pb++ effects, where Pb++ is added as PbCl2, however may be at least partially due to a Cl– or salt effect.Contribution from Purdue University Agricultural Experiment Station, West Lafayette, Indiana 47907. AES Journal No. 6934. This work was supported by federal funds from the National Science Foundation—RANN Program. 相似文献
8.
Masaru Uyeda Dr. Arnold L. Demain 《Journal of industrial microbiology & biotechnology》1987,1(6):341-347
Summary A cell-free extract from the thienamycin producer,Streptomyces cattleya, has been found to deacetylate the co-product,N-acetylthienamycin. The pH optimum of the reaction is 7.5. Due to the lability ofN-acetylthienamycin, we used thed andl forms of the synthetic substrateN-chloroacetylvaline. We found that the enzyme is anl-deacetylase, has a molecular weight of 58 000, is stable up to 40°C, acts optimally at 45°C, is stable at pH 5–8, is not activated by divalent metal ions and is inhibited by Hg++, Cu++ andp-chloromercuribenzoate. This is the first report of an extract from a carbapenem producer which carries out the deacetylation ofN-acetylthienamycin, suggesting that the acetylated derivative is a precursor of thienamycin.Abbreviations THM
thienamycin
- N-AcTHM
N-acetylthienamycin
- CFE
cell-free extract
- N-Cl-Ac-l-Val
N-chloroacetyl-l-valine
- N-Cl-Ac-d-Val
N-chloroacetyl-d-valine 相似文献
9.
Bdellovibrio spp. strains 6-5-S, 100, 109 (Davis), and A3.12 multiply in the presence of viable but non-proliferating or heat-killed (70
or 100 C, 10 min; 121 C, 5 min) cells ofSpirillum serpens strain VHL suspended in buffers supplemented with Ca++ and/or Mg++. Ca++ (optimal, 2 × 10−3
m) and Mg++ (optimal, 2 × 10−5
m) independently stimulate the groth of bdellovibrios: additive effects are noted. Multiplication ofBdellovibrio in the presence of Ca++ and Mg++ is associated with the release into the culture supernatant solution of UV-absorbing materials and of amino sugars (presumably
by activating or stabilizing lytic enzymes). The growth rate ofBdellovibrio strain 6-5-S in suspensions of heat-killed host cells is lower than in living but non-proliferating host cells.
Bdellovibrio spp. strains 100, 109 (Davis), 109 (Jerusalem), A3.12, and 6-5-S all require added Ca++ for growth in cell suspensions of homologous or heterologous host bacteria which have been grown in minimal medium.Bdellovibrio sp. strain 109 (Jerusalem) is capable of growing in the presence of the low level of Ca++ boundin situ to the cells of its host,E. coli B, when the host cells had been cultivated in a complex medium but not when the host cells had been grown in a Ca++-depleted minimal medium (except when Ca++ is added). Addition of ethylenediaminetetraacetic acid (0.01m) preventsBdellovibrio growth, which is restored by addition of Ca++ and Mg++.
The nonparasitic growth ofBdellovibrio spp. strains 100, 109, A3.12, and 6-5-S in heat-killed cell suspensions only in the presence of added cations indicates that,
in this system, the cations are essential for activity of bacteriolytic and other enzymes and that they might also directly
affectBdellovibrio growth rather than — as may be the case in other systems of live host cells plusBdellovibrio — only indirectly by affecting attachment to the host cell, maintaining integrity of the host spheroplasts, and increasing
the burst size. 相似文献
10.
Summary Glucosyltransferase activity was extracted from maize pollen in distilled water. The enzymatic reaction required UDP-glucose, mercaptoethanol and Ca++, and had a pH optimum at 8.2. Either kampferol or quercetin served as a substrate. Michaelis-Menten constants obtained were 0.6×10-4 M for quercetin and 0.74×10-3M for UDP-glucose. Ammonium-sulfate precipitation of the enzyme gave a 4fold purification.Cooperative investigations, Plant Science Research Division, Agricultural Research Service, U. S. Department of Agriculture, and Missouri Agricultural Experiment Station, Columbia. Journal Series No. 6224. 相似文献
11.
Summary Germinating spores of the fungus Botryodiplodia theobromae incorporated guanine-8-C14 into both the nuclear DNA and mitochondrial DNA fractions. Ethidium bromide inhibited the synthesis of mitochondrial DNA without having a significant effect on nuclear DNA synthesis or on the rate and extent of spore germination. Rates of leucine and uracil incorporation and of oxygen uptake were not significantly affected by ethidium bromide until germination was nearly completed. Mitochondrial DNA synthesis is apparently not required for germination of the spores of B. theobromae but is probably essential to continued vegetative growth.Abbreviations DNA
deoxyribonucleic acid
- mit-DNA
mitochondrial DNA
- nuc-DNA
nuclear DNA
- RNA
ribonucleic acid
- EB
ethidium bromide
- Tris
tris (hydroxymethyl)aminomethane
Published with the approval of the Director as Paper No. 3331, Journal Series, Nebraska Agricultural Experiment Station. Research reported was conducted under Project No. 21-17. Paper No. 7877, Scientific Journal Series, Minnesota Agricultural Experiment Station. 相似文献
12.
Isolated cell walls of Clostridium botulinum type A strain 190L released an autolysin during autolysis of the cell walls. The autolysin was isolated from the cell walls, and partially purified 18.6-fold by ammonium sulfate precipitation, chromatography on DEAE-cellulose and gel filtration through Sephadex G-100. The purified preparation of the autolysin showed 2 major and 2 minor protein bands on Polyacrylamide gel electrophoresis. Some properties of the autolysin were examined using SDS-treated cell walls of the organisms as a substrate. The autolysin was active over a pH range of 6 to 8, with a maximum near pH 6.8. The lytic activity was stimulated by 10?4 M each of Co++, Mg++ and Ca++ in the order, whereas it was inhibited markedly by Cu++. Mercaptoethanol (10?4–10?3 M) significantly activated the lytic action. Trypsin and nagarse (10 μg/ml) also stimulated the lytic activity. The lytic spectrum of the autolysin toward the SDS-treated cell walls obtained from various types of C. botulinum and C. perfringens indicated a relatively high specificity. After treatment with hot formamide the cell walls of C. botulinum increased in susceptibility to the autolysin. 相似文献
13.
Summary The uptake of Ca and Sr by three-week old tomato (Lycopersicon esculentum) plants from solutions containing Ca++ and Sr++, and chelated Ca and Sr (CaL and SrL) was measured over a two-day period. The solution was double-labelled with Ca45 and Sr85. Two chelates, EDTA (ethylenediaminetetraacetic acid) and DTPA (diethylenetriaminepentaacetic acid) were used at five chelate-cation ratios. When the Ca and Sr content of the solution was held constant, addition of chelate reduced uptake. The reduction was greater with EDTA than with DTPA.The Ca/Sr ratio of uptake was used to measure the proportion of uptake as the chelated and unchelated species. The Ca++/Sr++ ratio was different from the CaL/SrL ratio in solution because of the different equilibrium reactions of Ca and Sr with L. Direct uptake of the CaL and SrL was indicated. In solutions where Ca++ = CaL, uptake of CaEDTA was 0.47 of uptake of Ca++ and uptake of CaDTPA was 0.95 of uptake of Ca++.Journal Paper No. 4969. Purdue University Agricultural Experiment Station, Lafayette, Indiana 47907. Contribution from the Department of Agronomy. This research was supported in part by the U.S. Atomic Energy Commission under Contract AT(11-1)-1495. 相似文献
14.
Summary Lyophilized and stored in a deep-freeze, the mycelial material was found to retain cis-aconitic decarboxylase activity unimpaired at the end of 2 months. Mycelia could be stored also in the frozen condition but after squeezing hard to remove as much of adherent water as possible. Extracts with maximum cis-aconitic decarboxylase activity were obtained when the frozen or better the lyophilized mycelia of Aspergillus terreus were ground in a mortar with phosphate buffer using pyrex glass powder as abrasive. Cis-aconitic decarboxylase was purified 25-fold by fractionation with ammonium sulfate, starting from extracts of the mycelia in phosphate buffer. The purified enzyme was considerably more stable than the crude extracts to storage and dialysis. The optimum pH was 5.8 using 0.2 m phosphate buffer; Km value was 5×10-3
m at pH 5.8 and 37°C. EDTA and 8-hydroxyquinoline activated the enzyme; all metals tested inhibited the enzyme, Zn++ and Cu++ leading to complete inactivation. Fluoride, arsenite and azide also inhibited the enzyme activity. 相似文献
15.
Lacaz-Vieira F 《The Journal of membrane biology》2000,178(2):151-161
The present study aimed to characterize the role of protein kinase C (PKC) on the dynamics of tight junction (TJ) opening
and closing in the frog urinary bladder. The early events of TJ dynamics were evaluated by the fast Ca++ switch assay (FCSA), which consisted in opening the TJs by removing basolateral Ca++ ([Ca++]
bl
), and closing them by returning [Ca++]
bl
to normal values. Changes in TJ permeability can be reliably gauged through changes of transepithelial electrical conductance
(G) determined in the absence of apical Na+. The FCSA allows the appraisal of drugs and procedures acting upon the mechanism controlling the TJs. The time courses of
TJ opening and closing in an FCSA were shown to follow single exponential time courses. PKC inhibition by H7 (100 μm) caused a reduction of the rate of junction opening in response to removing [Ca++]
bl
, without affecting junction closing, indicating that PKC is a key element in the control of TJ opening dynamics in this preparation.
H7 at 250 μm almost completely inhibits TJ opening in response to basolateral Ca++ withdrawal. Subsequent H7 removal caused a prompt inhibition release characterized by a sharp G increase which, however, once started cannot be stopped by H7 reintroduction, Ca++ being necessary to allow TJ recovery. A step rise of apical Ca++ concentration ([Ca++]
ap
) causes a reduction of the rate of TJ opening in a FCSA, an effect that is believed to be mediated by apical Ca++ entering the open TJs. The specific condition of having Ca++ only in the apical solution and the TJs located midway between the Ca++ source (apical solution) and the Ca++-binding sites presumably located at the zonula adhaerens, might configure a situation in which a control feedback loop is set up. A rise of [Ca++]
ap
during the phase of G increase in an FCSA causes a transient recovery of G followed by a subsequent escape phase where G increases again. Oscillations of G also appear in response to a rise of apical Ca++. Both escape and oscillations result from the properties of the TJ regulatory feedback loop. In conclusion, the present results
indicate that PKC plays a key role in TJ opening in response to extracellular Ca++ withdrawal without major effect on the reverse process. In addition, PKC inhibition by H7 not only prevents TJ opening in
response to basolateral Ca++ removal but induces a prompt blockade of TJ oscillations induced by apical Ca++, oscillations which reappear again when H7 is removed.
Received: 9 May 2000/Revised: 30 August 2000 相似文献
16.
A voltage-activated Ca++ channel has been identified in the apical membranes of cultured rabbit proximal tubule cells using the patch-clamp technique.
With 105 mm CaCl2 solution in the pipette and 180 NaAsp in the bath, the channel had a conductance of 10.4 ± 1.0 pS (n= 8) in on-cell patches, and 9.8 ± 1.1 pS (n= 8) in inside-out patches. In both on-cell and inside-out patches, the channel is active by membrane depolarization. For
this channel, the permeation to Ba++ and Ca++ is highly selective over Na+ and K+ (PCa(Ba):PNa(K) >200:1). The sensitivity to dihydropyridines is similar to that for L-type channels where the channel was blocked by nifedipine
(10 μm), and activated by Bay K 8644 (5 μm). When activated by Bay K 8644, the channel showed subconductance levels. Treatment with forskolin (12.5 μm), phorbol ester (1 μm), or stretching (40 cm water) did not activate this channel. These results indicate that this Ca++ channel is mostly regulated by membrane voltage, and appears to be an epithelial class of L-type Ca++ channel. As such, it may participate in calcium reabsorption during periods of enhanced sodium reabsorption, or calcium signaling
in volume regulation, where membrane depolarization occurs for prolonged periods.
Received: 1 April 1996/Revised: 5 August 1996 相似文献
17.
Summary The effects of stepwise concentration changes of K+ and HCO
3
–
in the basolateral solution on the basolateral membrane potential (V
bl) of proximal tubule cells of the doubly-perfusedNecturus kidney were examined using conventional microelectrodes. Apparent transference numbers were calculated from changes inV
bl after alterations in external K+ concentration from 1.0 to 2.5mm (t
K, 1.0–2.5), 2.5 to 10, and in external HCO
3
–
concentration (at constant pH) from 5 to 10mm (t
HCO3, 5–10), 10 to 20, or 10 to 50.t
K, 2.5–10 was 0.38±0.02 under control conditions but was sharply reduced to 0.08±0.03 (P>0.001) by 4mm Ba++. This concentration of Ba++ reducedV
bl by 9±1 mV (at 2.5 external K+). Perfusion with SITS (5×10–4
m) for 1 hr hyperpolarizedV
bl by 10±3 mV and increasedt
K, 2.5–10 significantly to 0.52±0.01 (P<0.001). Ba++ application in the presence of SITS depolarizedV
bl by 22±3 mV. In control conditionst
HCO3, 10–50 was 0.63±0.05 and was increased to 0.89±0.07 (P<0.01) by Ba++ but was decreased to 0.14±0.02 (P<0.001) by SITS. In the absence of apical and basolateral chloride, the response ofV
bl to bicarbonate was diminished but still present (t
HCO3, 10–20 was 0.35±0.03). Intracellular pH, measured with liquid ion-exchange microelectrodes, increased from 7.42±0.19 to 7.57±0.17 (P<0.02) when basolateral bicarbonate was increased from 10 to 20mm at constant pH. These data show that the effects of bicarbonate onV
bl are largely independent of effects on the K+ conductance and that there is a significant current-carrying bicarbonate pathway in the basolateral membrane. Hence, both K+ and HCO
3
–
gradients are important in the generation ofV
bl, and their relative effects vary reciprocally. 相似文献
18.
Summary Cadmium ion (Cd++) significantly increased potential difference (PD) and short-circuit current (SCC) across isolated frog skin when added to the outside Ringer's solution at 10–4, 10–3 and 5×10–3
m concentration. Resistance was reduced by 10–4
m Cd++ but not significantly changed by the higher concentrations. When SCC was first stimulated by vasopressin, 10–4 and 10–3
m Cd++ produced additive stimulation which was reversible by washing with Cd++-free Ringer's. If SCC was first stimulated by Cd++, further stimulation by vasopressin was additive with 10–4
m Cd++ but completely inhibited by 10–3
m Cd++. Elevating the calcium ion (Ca++) concentration of the outer Ringer's from 10–3
m to 5×10–3
m or 10–2
m prior to Cd++ treatment did not reduce the magnitude of SCC stimulation by Cd++. Removal of Ca++ from the outside Ringer's with 2×10–3
m EDTA increased SCC as predicted. Subsequent addition of 5×10–3
m Cd++ drastically reduced SCC below control levels while equimolar concentrations of Cd++ and EDTA reduced SCC only to control levels. These results suggest that Cd++ interacts with the components of the apical plasma membranes of epithelial cells which are associated with the stimulation of SCC by vasopressin and Ca++ removal and may be a useful probe for elucidating these components. 相似文献
19.
Kenneth D. Laser 《Protoplasma》1974,80(1-3):279-283
Summary The plastids in sieve tube members of the stamen vascular bundles ofSorghum bicolor, fixed in glutaraldehyde with postfixation in osmium tetroxide, are of the P-type containing cuneate crystalloids of a proteinaceous nature surrounded by a double envelope. Secondary inclusions are present in these P-type plastids. P-type plastids inSorghum often remain intact in the mature sieve tube members.This work was supported by a grant from the Iowa Agricultural and Home Economics Experiment Station, Ames, U.S.A. Project No. 1740 toHarry T.Horner, Jr., andNels R.Lersten and Project No. 1914 toHarry T.Horner, Jr. of the Department of Botany and Plant Pathology, Iowa State University, Ames, U.S.A. This work was completed by the author as part of the Ph. D. dissertation research. 相似文献
20.
Summary The rate of active K+ transport by the isolated lepidopteran midgut shows a rectangular hyperbolic relation to [K+] over the range 20 to 70mm K+ in the absence of any divalent cation. Addition of Ba++ to the hemolymph (K+ uptake) side introduces a linear component to the concentration dependence, such that active K– transport is decreased at [K+] of 55mm or less, but increased transiently at higher [K+]. As [Ba++] is increased over the range 2 to 8mm the linear component increases and the saturating component decreases; in 8mm Ba++ the concentration dependence is dominated by the linear component. The effect of Ba++ cannot easily be accounted for by simple competition with K+ for basal membrane uptake sites. Similar effects might be exercised by other alkali earth cations, since the concentration dependence of active K+ transport possesses a substantial linear component in solutions containing 5mm Ca++ and 5mm Mg++ (the alkali earth metal concentrations of standard lepidopteran saline). 相似文献