Observations on bud formation and proliferations on cytokinin-treated root segments of Ophioglossum petiolatum

1969 ◽  
Vol 47 (10) ◽  
pp. 1579-1583 ◽  
Author(s):  
R. L. Peterson
Keyword(s):  
Apical Cell ◽  
Root Apex ◽  
Leaf Primordia ◽  
Distilled Water ◽  
Water Control ◽  
Cortical Cells ◽  
Root Segments ◽  
Low Concentrations ◽  
High Concentrations ◽  
Intact Root

Root segments of the fern Ophioglossum petiolatum with either an intact root apex or with the apex removed were treated with distilled water (control) or a range of concentrations of kinetin or benzyladenine in aqueous solution. Buds initiated on segments treated with distilled water or low concentrations of cytokinins had an apical meristem consisting of an apical cell with derivatives and a few leaf primordia located immediately beneath an air cavity formed by the lysis of cortical cells of the parent root. There was little cortical proliferation associated with the initiation of these buds. However, application of cytokinins at relatively high concentrations induced considerable proliferation of root tissue and a concomitant organization of numerous apical meristems in this tissue. Each induced meristem was structurally similar to those initiated on control root segments or those treated with low concentrations of cytokinins with the exception that leaf primordia were not as readily visible. Groups of tracheid-like cells were present in the callus-like outgrowths and, in root segments treated with 10.0 mg/l kinetin, large starch-filled parenchyma cells were evident at the periphery of the proliferations.

Calcium-accumulating cells in the meristematic region of grapevine root apices

2003 ◽  
Vol 30 (6) ◽  
pp. 719 ◽  
Author(s):  
Richard Storey ◽  
R. Gareth Wyn Jones ◽  
Daniel P. Schachtman ◽  
Michael T. Treeby
Keyword(s):  
Primary Root ◽  
Outer Region ◽  
Root Apex ◽  
Root Tip ◽  
Cortical Cells ◽  
Major Cations ◽  
High Calcium ◽  
High Concentrations ◽  
Root Apices ◽  
Crystal Idioblast

Apical roots of grapevines were examined by cryo-SEM (scanning electron microscopy) and the intracellular distribution of Ca was demonstrated by X-ray microanalysis in different regions of the primary root. We show that large amounts of Ca are accumulated as raphide crystals in the vacuoles of specialised cortical cells (idioblast cells) of the root apex. These crystal idioblast cells appeared to form a discontinuous cone of cells in the outer region of the root meristem. The raphide crystals within these cells were less apparent in older regions of the root, 10–12 mm basipetal to the root tip. We suggest that the raphide crystals could initially act as another Ca sink involved in the regulation of Ca levels in root apices. In older regions of the root these cells are spaced at intervals around the periphery of the cortex and the subsequent disappearance of the raphides may be indicative of remobilisation, perhaps in the zone of elongation where cell wall synthesis occurs and Ca demand is high. Calcium-accumulating cells were also observed in the older regions of the root, forming endodermal protrusions extending into the cortex. These cells may play a part in regulating Ca delivery to the xylem stream by sequestration of Ca from the radial flow of water at the endodermis. The observed distribution of Ca in root apices was different from the other major cations (e.g. K) and anions (e.g. Cl) because high concentrations were localised to specific cells. We interpret the results in the context of a model of the dynamics of grapevine root growth and cell differentiation, and the temporal balance of solute supply from the protophloem and the external medium.

A biphasic effect of noradrenaline on renin release from rat juxtaglomerular cells in vitro is mediated by α1- and β-adrenoceptors

1992 ◽  
Vol 132 (1) ◽  
pp. 133-140 ◽  
Author(s):  
M. Takagi ◽  
K. Atarashi ◽  
H. Matsuoka ◽  
T. Sugimoto
Keyword(s):  
Dynamic Balance ◽  
Inhibitory Effect ◽  
Renin Release ◽  
Dependent Manner ◽  
Adrenergic Stimulation ◽  
Cortical Cells ◽  
Adrenoceptor Antagonist ◽  
Low Concentrations ◽  
High Concentrations

ABSTRACT The direct effect of noradrenaline on renin release from juxtaglomerular (JG) cells in vitro were investigated in a dynamic superfusion system of dispersed rat renal cortical cells. At low concentrations (1–100 nmol/l), noradrenaline stimulated renin release in a dose-dependent manner, while at higher concentrations (0·1–1 mmol/l) it inhibited renin release. The stimulatory effect of 0·1 μmol noradrenaline/l was completely blocked by a β-adrenoceptor antagonist, propranolol (0·1 μmol/l). When applied at concentrations of 1 μmol/l or 10 μmol/l, noradrenaline had no consistent effect on renin release, although 10 μmol noradrenaline/l had an inhibitory effect in the presence of propranolol (0·1 μmol/l). The inhibitory effect of noradrenaline (0·1 mmol/l) was converted to a stimulatory effect by the addition of an α1-adrenoceptor antagonist (bunazosin, 1 μmol/l), but was not altered by the addition of an α2-adrenoceptor antagonist (yohimbine, 1 μmol/l). These results indicate that low concentrations of noradrenaline directly stimulate renin release from JG cells by the activation of β-adrenoceptors, while high concentrations of nor-adrenaline inhibit renin release by the activation of α1-adrenoceptors. Accordingly, a dynamic balance may exist between β-adrenergic stimulation and α1-adrenergic depression of renin release. Journal of Endocrinology (1992) 132, 133–140

scholarly journals Disturbance cues in freshwater prey fishes: Does urea function as an ‘early warning cue’ in juvenile convict cichlids and rainbow trout?

2012 ◽  
Vol 58 (2) ◽  
pp. 250-259 ◽  
Author(s):  
Grant E. Brown ◽  
Christopher D. Jackson ◽  
Patrick H. Malka ◽  
Élisa Jacques ◽  
Marc-Andre Couturier
Keyword(s):  
Rainbow Trout ◽  
Early Warning ◽  
Background Noise ◽  
Prey Species ◽  
Antipredator Behaviour ◽  
Distilled Water ◽  
Water Control ◽  
Convict Cichlids ◽  
High Concentrations ◽  
Disturbance Cues

Abstract Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to (1) determine if urea can function as a disturbance cue in juvenile convict cichlids and rainbow trout and (2) determine if the background level of urea influences the behavioral response to a subsequent pulse of urea (‘background noise’ hypothesis). In the first series of trials, juvenile cichlids and trout were exposed to urea at varying concentrations (0 to 0.5 mg L-1 for cichlids and 0 to 1.0 mg L-1 for trout). Our results suggest that both cichilds and trout exhibited functionally similar responses to urea and conspecific disturbance cues and that increasing the concentration of urea results in an increase intensity of antipredator behaviour. In the second series of trials, we pre-exposed cichlids or trout to intermediate or high concentrations of urea (or a distilled water control) and then tested for the response to a second pulse of urea at at intermediate or high concentrations (versus a distilled water control). Our results demonstrate that pre-exposure to urea reduces or eliminates the response to a second pulse of urea, supporting the background noise hypothesis. Together, our results suggest that pulses of urea, released by disturbed or stressed individuals, may function as an early warning signal in freshwater prey species [Current Zoology 58 (2): 250–259 , 2012].

Freeze-fracture, freeze-etch complementary pairs of virus-infected cells reveal value of etching even when relatively high concentrations of cryoprotectants are used

1978 ◽  
Vol 36 (2) ◽  
pp. 136-137
Author(s):  
Russell L. Steere ◽  
Eric F. Erbe
Keyword(s):  
Plant Tissue ◽  
Phosphate Buffer ◽  
Infected Plant ◽  
Freeze Fracture ◽  
Distilled Water ◽  
Virus Infected Plant ◽  
Infected Cells ◽  
High Concentrations

It has been assumed by many involved in freeze-etch or freeze-fracture studies that it would be useless to etch specimens which were cryoprotected by more than 15% glycerol. We presumed that the amount of cryoprotective material exposed at the surface would serve as a contaminating layer and prevent the visualization of fine details. Recent unexpected freeze-etch results indicated that it would be useful to compare complementary replicas in which one-half of the frozen-fractured specimen would be shadowed and replicated immediately after fracturing whereas the complement would be etched at -98°C for 1 to 10 minutes before being shadowed and replicated.Standard complementary replica holders (Steere, 1973) with hinges removed were used for this study. Specimens consisting of unfixed virus-infected plant tissue infiltrated with 0.05 M phosphate buffer or distilled water were used without cryoprotectant. Some were permitted to settle through gradients to the desired concentrations of different cryoprotectants.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

The Action of an Aniline Derivative (AN 162) on Blood Coagulation and on Platelets

1971 ◽  
Vol 26 (01) ◽  
pp. 145-166
Author(s):  
E Deutsch ◽  
K Lechner ◽  
K Moser ◽  
L Stockinger
Keyword(s):  
Blood Coagulation ◽  
Citric Acid Cycle ◽  
Second Phase ◽  
Aniline Derivative ◽  
Acid Cycle ◽  
Enhancing Effect ◽  
Low Concentrations ◽  
Dual Action ◽  
High Concentrations ◽  
Induced Aggregation

Summary1. The aniline derivative AN 162, Donau Pharmazie, Linz, Austria, has a dual action on the blood coagulation: an anticoagulant and an coagulation enhancing effect.2. The anticoagulant action may only be demonstrated with high concentrations (over 1 X 10”3 M related to plasma) preferentially in PPP. It is partially caused by an inhibition of the endogenous way of generation of the prothrombin converting principle. In addition it is suggested that it interferes with the fibrinogen-fibrin reaction in a manner not yet understood.3. The coagulant action is caused by a greater availability of platelet constituents at low concentrations of AN 162 (over 1 × 10-4 M) and by the induction of a release reaction at higher concentrations. The platelet factors 3 and 4, serotonin, adenine, and acid phosphatase are released.4. AN 162 inhibits platelet aggregation. This inhibition can be demonstrated by the PAT of Breddin and in the stirred aggregation test of Born. It is more effective to inhibit the collagen-induced and the second phase of the adrenaline-induced aggregation than the ADP induced one. The platelet retention (test of Hellem) is also reduced.5. The action of AN 162 on the platelets is caused by a damage of the platelet membrane which becomes permeabel for both, soluble platelet constitutents and granula.6. AN 162 interferes with the energy metabolism of the platelets. It causes a loss of ATP, and inhibits the key-enzymes of glycolysis, citric acid cycle, fatty acid oxydation and glutathione reduction.7. AN 162 inhibits the growth of fibroblasts without influence on mitosis.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

Biological Mechanisms of H2S Formation in Sewer Pipes

1992 ◽  
Vol 26 (3-4) ◽  
pp. 907-914 ◽  
Author(s):  
A. Attal ◽  
M. Brigodiot ◽  
P. Camacho ◽  
J. Manem
Keyword(s):  
Suspended Solid ◽  
Urban Wastewater ◽  
Biological Mechanisms ◽  
Sewer Pipes ◽  
Sulfate Reducing ◽  
Biological Phenomena ◽  
Low Concentrations ◽  
Production Of Hydrogen ◽  
High Concentrations ◽  
Reducing Bacteria

The purpose of this study is to gain a better understanding of the biological phenomena involved in the production of hydrogen sulfide in urban wastewater (UWW) systems. It is found that the UWW itself naturally possesses the biomass needed to consume the sulfates. These heterotrophic sulfate-reducing bacteria populations, though immediately active in strict anaerobic conditions, are present only in very low concentrations in the UWW. A concentration of them was studied within the pressure pipes, in the form of deposits, and this justifies the high concentrations of sulfides measured in certain wastewater networks. There are two reasons why the ferrous sulfate used as a treatment in any wastewater networks should not cause the production of additional sulfides. Firstly, the sulfate consumption kinetics are always too slow, relative to the residence time of the water in the pipe, for all of the sulfates to be consumed anyway. Secondly, the amount of assimilable carbon, soluble carbon, and carbon from suspended solid (SS) hydrolysis is insufficient.

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