Hi everyone,
I am a master student in medicine.
in the paper " Late Ca2+ Sparks and Ripples During the Systolic Ca2+ Transient in Heart Muscle Cells", I dont understand how to measure the distance from T-tubule to Late calcium spark (figure 1D). is there anyone can explain more detail about the figure 2D in this article for me please?
Thank you for taking time resolving my issues.
and this is the context:
" A simple, obvious, explanation for the genesis of the LCSs would be that they arise from jSR that was either not activated during the upstroke of the Ca2+ transient or was uncoupled or orphaned17 from t-tubules (which carry the AP to the cell interior). To examine this idea, we labeled t-tubules (Figure 1D) and measured the Euclidian distance to the LCS centroid (Figure 1E) and compared the latencies for the upstroke of the Ca2+ transient at LCS sites to overall Ca2+ transient latency (Figure 1F). Perhaps unexpectedly, LCS occurred close to t-tubules and at positions where the Ca2+ transient developed with a shorter than average latency (P
Q is interesting from a Signal Analysis View. Hope follwing helps. 1.High sensitivity identifies additional LCS(Ca2+0 )
2. 1A left typical transient ... 1A right enhanced version
3. 1B shows increased ampl compared with 1C duration of transient is apprx same.
4. LCS uncoupled from t -tubules? is the question.
5 Solution :
5.1 label tubules 1D
5.2 meaure dustaceoft tubules to Lcscentroids .result 1E
5.3conclusion: LCS is close to t-tubules. and is due to short latency period of activation. so LCS is not orphaned but well coupled.
6. Useful descriptins : 6.1 from :https://homepages.inf.ed.ac.uk/rbf/HIPR2/label.htm
" labeling:: Connected component labeling works by scanning an image, pixel-by-pixel (from top to bottom and left to right) in order to identify connected pixel regions, i.e. regions of adjacent pixels which share the same set of intensity values V. (For a binary image V={1}; however, in a graylevel image V will take on a range of values, for example: V={51, 52, 53, ..., 77, 78, 79, 80}.) Connected component labeling works on binary or graylevel images and different measures of connectivity are possible. However, for the following we assume binary input images and 8-connectivity. The connected components labeling operator scans the image by moving along a row until it comes to a point p (where p denotes the pixel to be labeled at any stage in the scanning process) for which V={1}. When this is true, it examines the four neighbors of p which have already been encountered in the scan (i.e. the neighbors (i) to the left of p, (ii) above it, and (iii and iv) the two upper diagonal terms). Based on this information, the labeling of p occurs as follows: If all four neighbors are 0, assign a new label to p, else if only one neighbor has V={1}, assign its label to p, else if more than one of the neighbors have V={1}, assign one of the labels to p and make a note of the equivalences. After completing the scan, the equivalent label pairs are sorted into equivalence classes and a unique label is assigned to each class. As a final step, a second scan is made through the image, during which each label is replaced by the label assigned to its equivalence classes. For display, the labels might be different graylevels or colors. "
4,2 Centoids : Centroid Eucliduan distance = sqrt ((x1c-x2c)^2+ (y1c -y2c)) for a nice explanaion ; https://stackoverflow.com/questions/25984552/explanation-of-matlabs-bwlabel-regionprops-centroid-functions Cheers
Let us try again.
1. It seems the authors have identified orphaned Lcs.
2. They have verified that these Lcs have same response
Time to reach the max and also spatial spread is approx same
As non orphaned ones.
3. Now the question is Are the orphaned Lcs connected
To the t-tubules. ?
4 The answer is that they are located very near the t-tubules
This is proved by checking the distance between them and
identified orphaned Lcs.This is done by finding distance between.
orphaned Lcs and t-tubules using the centroids of these segments.
5. Probably confocal image with different filters are able to localize
The t-tubules.
Hope this helps else is it possible to spell out clearly your
confusion
Good Luck
Cheers
greeting respected Prof. Narasim Ramesh
Thank you again.
I understood the authors rationale and question, but I dont understand the figure I mentioned. "The median distance to nearest t-tubule was shorter for LCS sites than the cell average distance". what is the cell average distance? How to determine it?
And in figure 2b, and c, why the half-time is 475 ms? because as I know, the half of transient it is The half time is the full duration at half-maximum of the Ca transient i.e. the time between 50% of the Ca transient upstroke and 50% of decay. in this figure it must be around 700ms not 475?
Let us take it a step at a time
I think he has used the following deff. He has approx right
side of curve with exponential . Then we get 750 - 300=450aprx.
Regarding half time I found this deff :
1. From :
https://en.wikipedia.org/wiki/Half_time_(physics)
"The 'half time' is the time taken by a quantity to reach one half of its extremal value, where the rate of change is proportional to the difference between the present value and the extremal value (i.e. in exponential decay processes). It is synonymous with half-life, but used in slightly different contexts.
The diagram shows the increase in the quantity (red) in response to a step-change in the motive force that changes it (blue). The time-axis is in multiples of the half time. It can be seen that the quantity increases to one-half of its final value after one half time, to three-quarters after two half times, to seven-eighths after three half times, and so on.
The relationship between the quantity (Q) and time (t) is described by the mathematical formula:
Q ( t ) = Q f ( 1 − e − λ t ) {\displaystyle Q(t)=Q_{\mathrm {f} }(1-e^{-\lambda t})} 📷
where Qf is the extremal value and λ is a constant, approximately equal to 0.69 divided by the half time – more precisely: loge(2) / (half time).
Where the quantity decreases in response to a step-decrease in the motive force that changes it, the curve is mirrored in the time-axis and may be referred to as exponential decay. '
//xxx
also see
" In electronics, when a capacitor is charged or discharged via a resistor, the voltage on the capacitor follows the above formula, with the half time approximately equal to 0.69 times the time constant, which is equal to the product of the resistance and the capacitance. "
2.Q what is the cell average distance? How to determine it?
I think he means distance between successie t-tubules.
Found by centroid distances between t-tubules...see 1D middle.
Hope it helps . Feel free to discuss. Imagej might be useful tool.
Cheers
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