Przemysław Zakrzewski

Przemysław Zakrzewski
Nicolaus Copernicus University | umk · Department of Cell Biology

Doctor of Philosophy

About

8
Publications
100,750
Reads
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63
Citations
Citations since 2016
7 Research Items
63 Citations
2016201720182019202020212022051015
2016201720182019202020212022051015
2016201720182019202020212022051015
2016201720182019202020212022051015
Additional affiliations
August 2020 - present
University of Bristol
Position
  • Research Associate
March 2018 - July 2020
University of Cambridge
Position
  • PhD Student
June 2015 - October 2016
Nencki Institute of Experimental Biology
Position
  • PhD Student
Education
October 2012 - June 2014
Nicolaus Copernicus University
Field of study
  • Biotechnology
October 2011 - June 2014
Nicolaus Copernicus University
Field of study
  • Biomedical chemistry
October 2009 - June 2012
Nicolaus Copernicus University
Field of study
  • Biotechnology

Publications

Publications (8)
Article
Full-text available
A useful model for determining the mechanisms by which actin and actin binding proteins control cellular architecture is the Drosophila melanogaster process of spermatogenesis. During the final step of spermatogenesis, 64 syncytial spermatids individualized as stable actin cones move synchronously down the axonemes and remodel the membranes. To ide...
Article
Full-text available
Spermiogenesis is the final stage of spermatogenesis, a differentiation process during which unpolarized spermatids undergo excessive remodeling that results in the formation of sperm. The actin cytoskeleton and associated actin-binding proteins play crucial roles during this process regulating organelle or vesicle delivery/segregation and forming...
Article
Full-text available
During spermiogenesis in mammals actin filaments and a variety of actin-binding proteins are involved in the formation and function of highly specialized testis-specific structures. Actin-based motor proteins, such as myosin Va and VIIa, play a key role in this complex process of spermatid transformation into mature sperm. We have previously demons...
Article
Full-text available
Myosin VI (MYO6) is an actin-based motor that has been implicated in a wide range of cellular processes, including endocytosis and the regulation of actin dynamics. MYO6 is crucial for actin/membrane remodeling during the final step of Drosophila spermatogenesis, and MYO6-deficient males are sterile. This protein also localizes to actin-rich struct...
Article
Full-text available
Calcium (Ca(2+)) plays essential roles in generative reproduction of angiosperms, but the sites and mechanisms of Ca(2+) storage and mobilization during pollen-pistil interactions have not been fully defined. Both external and internal Ca(2+) stores are likely important during male gametophyte communication with the sporophytic and gametophytic cel...
Article
Full-text available
Myosin VI (MVI) is a versatile actin-based motor protein that has been implicated in a variety of different cellular processes, including endo- and exocytic vesicle trafficking, Golgi morphology, and actin structure stabilization. A role for MVI in crucial actin-based processes involved in sperm maturation was demonstrated in Drosophila. Because of...
Article
Full-text available
Main conclusion: Calreticulin is involved in stabilization of the tip-focused Ca (2+) gradient and the actin cytoskeleton arrangement and function that is required for several key processes driving Petunia pollen tube tip growth. Although the precise mechanism is unclear, stabilization of a tip-focused calcium (Ca(2+)) gradient seems to be critica...
Article
Full-text available
Myosin VI (MVI), an actin-based molecular motor, is believed to have unique functions in eukaryotic cells, because it is the only myosin shown to move toward the pointed end of actin filaments, in the opposite direction of all other myosins. Given some unusual structural and kinetic properties of MVI, many models of its functioning in variety cellu...

Questions

Questions (4)
Question
Hello everyone!
I have a theoretical problem with a statistical analysis. I was looking a lot at different fora but I could not find an easy explanation for my problem.
I want to compare means of two groups of data. In a simple case, I would use "t-test". However, in each group, I have few measurements for each individual. First, I wanted to measure a mean for every individual in a group, then compare the means of groups, but I know that it is not a good idea (mean of means/average of averages...).
For example how to compare this data sets:
GROUP A:
Individual 1: 5, 6, 7
Individual 2: 5, 7, 7, 6
Individual 3: 6, 7, 7
GROUP B:
Individual 1: 4, 5, 4
Individual 2: 7, 8, 6
Individual 3: 4, 3, 4, 2
You can imagine two groups of people. A - treated, B - untreated. In each group there are 3 people and some variable were measured with 3-4 repeats.
As you can see there are two groups made of few individuals for which few repeated measurements were made. I would like to compare two groups using means calculated for individuals, not measure simple mean for the whole group.
I have read a lot about pooled data, weighed means etc. but I still do not know how to perform t-test in that case (or another).
I hope you can help me!
Question
Hello everyone! I would like to ask, how to quench autofluorescence of glutaraldehyde fixed specimen. I always perform standard fixation for immunocytochemistry (4%FA and 0,5%GA) but this time I see, that my specimens embedded in LR Gold is more yellow than usual, which means that GA concentration was higher (I do not have any idea how it is possible, but mistakes happen...). After sectioning I see, that sections have very high autofluorescence in every channel. I found that it is possible to perform immunofluorescence labelling on glutaraldehyde fixed cell after reducing free aldehyde groups using NaBH4, however we do not have this reagent in our lab. I'm thinking whether it is possible to reduce glutaraldehyde using different reducing agent like oxalic acid, or thiosulfate? I'm also thinking about oxidation of aldehyde groups to -COOH, f. ex. with hydrogen peroxide. Actually, I've tried with 3% H2O2, and all fluorescence disappeared, however I don't know if that didn't affect my specimen in some way (I don't want to waste my antibodies before consulting with someone). Glycine and ammonium chloride quenching didn't work.
I would be very greatful for any help provided.
Question
I would like to embbed mouse tissue (testis) in LR Gold for immunogold analysis, however I do not have UV light, which is crucial for resin polymerization. However I know that polymerization without ultraviolet light is also possible. I always penetrate tissue with 3:1, 1:1, 1:3 alcohol:LR Gold solutions, then I keep tissue in 100% LR Gold, and finally I mix LR Gold with catalyst (benzyl peroxide), and place the tissue in gelatin capsules. I keep specimens at 4 C. degrees and resin do polymerize. However, when I place the tissue in LR Gold/catalyst solution polymerization is quite fast, and the resin is not able to penetrate the tissue enough. As a result I receive hard resin block with soft unpolimerized tissue. Could someone tell me what to do? I wanted to say, that I successfully polymerized LR Gold in this way, however I know that this approach is not always working. I would be really greatful for any help. Maybe someone could give me whole protocol for animal tissue LR Gold embedding?
Question
I am trying for a long time to localize loosely bound calcium ions in Drosophila tissues using pyroantimonate precipitation for TEM analysis, however every time I do not have any precipitates. I do not know if it is caused by wrong concentration of PPA or I do something wrong with pH of buffers. Is any one could give me FULL protocol for PPA precipitation in animal tissue including preparation of PPA solution? Currently I am trying do this using potassium phosphate buffer, pH 7.4, I add PPA to fixative. I would be greatful for any suggestions.

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