Determination of secretory vesicle production rates by dictyosomes in pollen tubes of Tradescantia using cytochalasin D

1981 ◽  
Vol 49 (1) ◽  
pp. 261-272 ◽  
Author(s):  
J.M. Picton ◽  
M.W. Steer
Keyword(s):  
Turnover Rate ◽  
Secretory Vesicle ◽  
Pollen Tubes ◽  
Cytochalasin D ◽  
Wall Material ◽  
Secretory Vesicles ◽  
Size Distributions ◽  
Visible Effect

Pollen tubes of Tradescantia were grown in vitro and exposed to 0.3 microgram/ml cytochalasin D for 5 or 10 min. Fine-structural observations revealed no visible effect of the drug on the organelles. Stereological analysis, using a method recently developed by Rose (1980) to obtain sphere size-distributions corrected for section thickness, revealed substantial increase in the number of secretory vesicles present in the cytoplasm around the dictyosomes. Equating the rate of vesicle accumulation with the rate of vesicle production, a total of 5388 vesicles per minute are formed by a growing tube. This corresponds to 2.4 vesicles per minute per dictyosome, and a turnover rate of 3.7 min for a single dictyosome cisterna, or about 15–18.5 min for a complete dictyosome. The calculated vesicle production rate agrees well with that required to sustain the observed growth rate of such tubes, based on the addition of membrane or wall material to the tube tip.

scholarly journals Plant AP180 N-Terminal Homolog Proteins Are Involved in Clathrin-Dependent Endocytosis during Pollen Tube Growth in Arabidopsis thaliana

2019 ◽  
Vol 60 (6) ◽  
pp. 1316-1330 ◽  
Author(s):  
Minako Kaneda ◽  
Chlo� van Oostende-Triplet ◽  
Youssef Chebli ◽  
Christa Testerink ◽  
Sebastian Y Bednarek ◽  
...  
Keyword(s):  
Cell Wall ◽  
Pollen Tube ◽  
Membrane Trafficking ◽  
Pollen Tubes ◽  
Wall Material ◽  
Knockout Mutant ◽  
Cell Wall Assembly ◽  
Morphological Defects ◽  
Fluorescent Tagging

Abstract Polarized cell growth in plants is maintained under the strict control and exquisitely choreographed balance of exocytic and endocytic membrane trafficking. The pollen tube has become a model system for rapid polar growth in which delivery of cell wall material and membrane recycling are controlled by membrane trafficking. Endocytosis plays an important role that is poorly understood. The plant AP180 N-Terminal Homolog (ANTH) proteins are putative homologs of Epsin 1 that recruits clathrin to phosphatidylinositol 4, 5-bisphosphate (PIP2) containing membranes to facilitate vesicle budding during endocytosis. Two Arabidopsis ANTH encoded by the genes AtAP180 and AtECA2 are highly expressed in pollen tubes. Pollen tubes from T-DNA inserted knockout mutant lines display significant morphological defects and unique pectin deposition. Fluorescent tagging reveals organization into dynamic foci located at the lateral flanks of the pollen tube. This precisely defined subapical domain coincides which clathrin-mediated endocytosis (CME) and PIP2 localization. Using a liposome-protein binding test, we showed that AtECA2 protein and ANTH domain recombinant proteins have strong affinity to PIP2 and phosphatidic acid containing liposomes in vitro. Taken together these data suggest that Arabidopsis ANTH proteins may play an important role in CME, proper cell wall assembly and morphogenesis.

scholarly journals Submaximal Responses in Calcium-triggered Exocytosis Are Explained by Differences in the Calcium Sensitivity of Individual Secretory Vesicles

1998 ◽  
Vol 112 (5) ◽  
pp. 559-567 ◽  
Author(s):  
Paul S. Blank ◽  
Myoung-Soon Cho ◽  
Steven S. Vogel ◽  
Doron Kaplan ◽  
Albert Kang ◽  
...  
Keyword(s):  
Calcium Sensitivity ◽  
Secretory Vesicle ◽  
Secretory Vesicles ◽  
Calcium Dependent ◽  
Sea Urchin Egg ◽  
Dependent Inactivation ◽  
Graded Response ◽  
Vesicle Exocytosis

A graded response to calcium is the defining feature of calcium-regulated exocytosis. That is, there exist calcium concentrations that elicit submaximal exocytotic responses in which only a fraction of the available population of secretory vesicles fuse. The role of calcium-dependent inactivation in defining the calcium sensitivity of sea urchin egg secretory vesicle exocytosis in vitro was examined. The cessation of fusion in the continued presence of calcium was not due to calcium-dependent inactivation. Rather, the calcium sensitivity of individual vesicles within a population of exocytotic vesicles is heterogeneous. Any specific calcium concentration above threshold triggered subpopulations of vesicles to fuse and the size of the subpopulations was dependent upon the magnitude of the calcium stimulus. The existence of multiple, stable subpopulations of vesicles is consistent with a fusion process that requires the action of an even greater number of calcium ions than the numbers suggested by models based on the assumption of a homogeneous vesicle population.

scholarly journals Calcium Dependencies of Regulated Exocytosis in Different Endocrine Cells

2011 ◽  
pp. S29-S38
Author(s):  
J. DOLENŠEK ◽  
M. SKELIN ◽  
M. S. RUPNIK
Keyword(s):  
Pancreatic Beta Cells ◽  
Endocrine Cells ◽  
Secretory Vesicle ◽  
Pituitary Cells ◽  
Secretory Vesicles ◽  
Regulated Exocytosis ◽  
Vesicle Exocytosis ◽  
Adrenal Chromaffin ◽  
Endocrine Tissues

Exocytotic machinery in neuronal and endocrine tissues is sensitive to changes in intracellular Ca2+ concentration. Endocrine cell models, that are most frequently used to study the mechanisms of regulated exocytosis, are pancreatic beta cells, adrenal chromaffin cells and pituitary cells. To reliably study the Ca2+ sensitivity in endocrine cells, accurate and fast determination of Ca2+ dependence in each tested cell is required. With slow photo-release it is possible to induce ramp-like increase in intracellular Ca2+ concentration ([Ca2+]i) that leads to a robust exocytotic activity. Slow increases in the [Ca2+]i revealed exocytotic phases with different Ca2+ sensitivities that have been largely masked in step-like flash photo-release experiments. Strikingly, in the cells of the three described model endocrine tissues (beta, chromaffin and melanotroph cells), distinct Ca2+ sensitivity ‘classes’ of secretory vesicles have been observed: a highly Ca2+-sensitive, a medium Ca2+-sensitive and a low Ca2+-sensitive kinetic phase of secretory vesicle exocytosis. We discuss that a physiological modulation of a cellular activity, e.g. by activating cAMP/PKA transduction pathway, can switch the secretory vesicles between Ca2+ sensitivity classes. This significantly alters late steps in the secretory release of hormones even without utilization of an additional Ca2+ sensor protein.

scholarly journals Structure of the generative cell wall complex after freeze substitution in pollen tubes of Nicotiana and Impatiens

1987 ◽  
Vol 88 (3) ◽  
pp. 373-378
Author(s):  
M. CRESTI ◽  
S. A. LANCELLE ◽  
P. K. HEPLER
Keyword(s):  
Cell Wall ◽  
Plasma Membranes ◽  
Generative Cell ◽  
Pollen Grains ◽  
Freeze Substitution ◽  
Pollen Tubes ◽  
Wall Material ◽  
Cell Cytoplasm ◽  
Stage Of Development

The mature generative cell in pollen grains and pollen tubes is surrounded by a wall complex that includes two plasma membranes, one facing the generative cell cytoplasm and one facing the vegetative cell cytoplasm, and usually some intervening wall material. After conventional chemical fixation, the two plasma membranes are very uneven and often appear to be joined, giving the impression that numerous plasmodesmata connect the vegetative and generative cells. These areas alternate with swollen, distorted areas, which give the wall complex the appearance of being composed of a chain of vesicles. Utilizing rapid freeze fixation and freeze substitution, we have re-examined the ultrastructure of the generative cell wall complex from pollen tubes grown in vitro, and the differences are striking. The two plasma membranes are very smooth and closely appressed to a layer of wall material. Occasionally the wall complex contains swollen areas, or varicosities, and these may contain pockets of lightly stained material, but again the surrounding plasma membranes are tightly appressed to these areas. Plasmodesmata are not seen, but this does not eliminate the possibility that they may exist at an earlier stage of development.

Determination of in vitro „anti-aging„-effects of Ganoderma pfeifferi

Planta Medica ◽  
2010 ◽  
Vol 76 (12) ◽  
Author(s):  
W Jülich ◽  
J Pörksen ◽  
H Welzel ◽  
U Lindequist
Keyword(s):  
Aging Effects

In vitro determination of the skin anti-aging potential of eleven South African plants

Planta Medica ◽  
2013 ◽  
Vol 79 (13) ◽  
Author(s):  
GN Ndlovu ◽  
G Fouche ◽  
W Cordier ◽  
V Steenkamp ◽  
M Tselanyane
Keyword(s):  
South African ◽  
South African Plants ◽  
African Plants

A Molecular Approach to Immunoscintigraphy: A Study of the T-Antigen Conformation on the Surface of Tumors

1987 ◽  
Vol 26 (01) ◽  
pp. 1-6 ◽  
Author(s):  
S. Selvaraj ◽  
M. R. Suresh ◽  
G. McLean ◽  
D. Willans ◽  
C. Turner ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Tumor Cell ◽  
T Antigen ◽  
Human Carcinomas ◽  
Animal Tumor ◽  
Synthetic Antigens

The role of glycoconjugates in tumor cell differentiation has been well documented. We have examined the expression of the two anomers of the Thomsen-Friedenreich antigen on the surface of human, canine and murine tumor cell membranes both in vitro and in vivo. This has been accomplished through the synthesis of the disaccharide terminal residues in both a and ß configuration. Both entities were used to generate murine monoclonal antibodies which recognized the carbohydrate determinants. The determination of fine specificities of these antibodies was effected by means of cellular uptake, immunohistopathology and immunoscintigraphy. Examination of pathological specimens of human and canine tumor tissue indicated that the expressed antigen was in the β configuration. More than 89% of all human carcinomas tested expressed the antigen in the above anomeric form. The combination of synthetic antigens and monoclonal antibodies raised specifically against them provide us with invaluable tools for the study of tumor marker expression in humans and their respective animal tumor models.

Storage of Human Blood Platelets

1974 ◽  
Vol 32 (02/03) ◽  
pp. 405-416 ◽  
Author(s):  
M. R Hardeman ◽  
Carina J L. Heynens
Keyword(s):  
Storage Temperature ◽  
Platelet Rich Plasma ◽  
Blood Platelets ◽  
Storage Period ◽  
Serotonin Uptake ◽  
Hypotonic Shock ◽  
Glycolytic Intermediates

SummaryStorage experiments were performed at 4°, 25° and 37° C with platelet-rich plasma under sterile conditions. In some experiments also the effect of storing platelets at 4° C in whole blood was investigated.Before, during and after three days of storage, the platelets were tested at 37° C for their serotonin uptake and response to hypotonic shock. In addition some glycolytic intermediates were determined.A fair correlation was noticed between the serotonin uptake and hypotonic shock experiments. Both parameters were best maintained at 25° C. Also platelet counting, performed after the storage period, indicated 25° C as the best storage temperature. Determination of glycolytic intermediates did not justify any conclusion regarding the optimal storage temperature. Of the various anticoagulants studied, ACD and heparin gave the best results as to the serotonin uptake and hypotonic shock response, either with fresh or stored platelets. The use of EDTA resulted in the lowest activity, especially after storage.The results of these storage experiments in vitro, correspond well with those in vivo reported in the literature.

Sign in / Sign up

Export Citation Format

Share Document