12 votes
Accepted

Why are cell lines frozen in vapor phase?

The storage itself can be done both in the liquid and also in the vapor phase in the liquid nitrogen. Both have their advantages and disadvantages. In my experience there are two main reasons why ...
  • 50.5k
10 votes

Henrietta Lacks and HeLa cells

The cells never died in the sense that they kept replicating, individual cells still died. They were safely cultured in petri dishes before Henrietta Lacks died. The cells came from a tumor that ...
  • 5,328
8 votes
Accepted

Origin of term ‘confluency’ in cell culture

Besides the etymologic explanation that @aandreev gave, in cell culture this term is commonly used to describe the density of adherent cells and it is used as a measure of their proliferation. It is ...
  • 50.5k
8 votes

A biological system to measure time

There are lots of biological clocks, or clocks made of biological components. The circadian clock is an important, though complicated, example. There are excellent engineered clocks that form some of ...
7 votes
Accepted

Why is glycerol supplied/used as 87% solution?

Typically, a glycerol stock will have a final concentration of 10-20% of glycerol. Glycerol is highly viscous. Pipetting higher concentrations of glycerol is difficult (especially for smaller volumes)....
  • 35.2k
6 votes
Accepted

Why do epithelial cells arrest in response to serum?

TGF-beta would be a good candidate. To cite: "TGF-β inhibits G1/S progression in a variety of eukaryotic cell types. Among these, untransformed epithelial cells are particularly sensitive to the ...
  • 116
6 votes

Tumour cell injection into a mice

You should not be asking random people on the internet about this. Talk to your lab safety people. Get detailed instructions on handling requirements. As for the hood, again, do not ask here, ask your ...
  • 14.1k
6 votes

Is it safe to work with HeLa cells?

Most guidelines for HeLa (and most cells of human origin) say they should be kept at a BSL2 level. For example, from a 2007 publication in Applied Biosafety: Work with cell cultures from human or ...
  • 14.1k
5 votes
Accepted

What type of flask should I use to culture NTERA2 embryonic cancer stem cells?

I found a protocol by ATCC for NTERM2 cells, and it didn't mention any specific flask, so any cell culture flask would do. Since ATCC is basically a cell culture bank I trust that their protocol is ...
  • 3,098
5 votes
Accepted

Are HeLa cells edible?

I think HELA cells are edible, although from moral point of view this would be cannibalism. Despite they are cancer cells, they are safe for foreign organism, because any ate matter is destroyed. ...
  • 548
5 votes

Do I need to serially dilute E. coli cultures for optical density measures?

One is not normally required to serially dilute E. coli cultures for spectrophotometric measurements, at least in the experiments where the OD value is important. For most protein expression work, ...
  • 9,414
5 votes

Decreasing signals in assay measurements

Freeze-thaw cycles are often suspected of causing degradation in organic molecules 1,2. My first guess would be that your fluorophore is breaking down due to those repeated cycles. Alternatively, you ...
  • 5,502
5 votes

Appropriate cell lines to study depression

tl;dr there is no 'depression' cell line. Cell lines would be suited for studying pharmacology, cellular or molecular mechanisms, none of which are depression. Depression also has no good correlates ...
  • 5,979
4 votes

Why do some protocols require prewarming a liquid medium before inoculating?

It's because E.coli BL21(DE3) are competent cells. The competent is the key here as the cells were chemically treated so the transfection can be performed by heat-shock with high efficiency. This ...
  • 2,873
4 votes

Studying effects of alcohol on cells

Based on T Abraham's answer, a hemocytometer would work. However, a hemocytometer requires a microscope, but if you are in a cell lab, you probably have access to a microscope. I would recommend using ...
  • 5,328
4 votes

Studying effects of alcohol on cells

Great idea! It seems that this research has been done before and your hypothesis is correct, but testing a wide variety of alcohols and testing your hypothesis for each one of them would be a great ...
  • 3,079
4 votes
Accepted

Does a specific blood group enhance the Plasmodium growth?

It is a well documented observation that Plasmodium (vivax and knowlesi) infection is dependent on the Duffy blood groups [1]. Individuals lacking the Duffy antigens (Fya and Fyb) have lower ...
  • 35.2k
4 votes
Accepted

Do bacteria grow on pure dry glucose?

Bacteria or other microorganisms cannot really grow on anhydrous (totally dry) glucose because they need water. However, they can remain there and cause contamination. Even if you haven't actually ...
  • 35.2k
4 votes
Accepted

Is there a difference between "cell line" and "cell strain"?

"Strain", in general, is usually used for whole organisms (whether they are unicellular or multicellular). For example, there are mouse strains. "Cell line", on the other hand, is a very specific ...
  • 35.2k
4 votes

Trypsin and Cell Surface Receptors

Yes. Trypsin cleaves proteins and can do so quite indiscriminately if left on for very long. Trypsin is primarily used to cleave the proteins that cells use to adhere to each other and the plate in ...
  • 1,309
4 votes
Accepted

Mold identification

I initially figured it was condensation from the agar. But it is not on your lid and you said you suspected humidity was low. I found this here http://www.gettyimages.ca/detail/photo/mold-...
  • 2,956
4 votes
Accepted

Why do coliform bacteria smell so bad?

E. coli and other bacteria metabolize tryptophan into odoriferous skatole and other indole compounds. If you're culturing these organisms in medium that contains tryptophan, that may be what you're ...
4 votes

What is the meaning of harboring cryptic in below sentence?

Harbouring, using harbour as a verb and in this meaning containing/hiding (see 3rd and 4th definitions at Harbour) Cryptic = hidden/difficult to find - this is how the word is often used in biology, ...
  • 8,774
3 votes

Origin of term ‘confluency’ in cell culture

con- (com-) is prefix that usually means "togetherness", joining. Root fluency/fluent comes from latin fluere, to flow. Source: Google's definitions for con- and fluency (information scraped from OUP)...
3 votes

Studying effects of alcohol on cells

For assaying effect of alcohol on cell growth:     Prokaryotic Cells Take ~5ml medium (LB for E.coli) in test-tubes/plastic tubes and add appropriate concentration of alcohol(s) ...
  • 35.2k
3 votes
Accepted

Staining cells for FACS at 4 degrees or ambient temperature

You have several questions, please try to limit your posts to one question each. That being said, I'll try to address each of your concerns. Does the cold cause these cells to apoptose? No. The ...
  • 15.1k
3 votes

Is it possible to grow E. coli K12 with algal amino acids as the sole carbon source?

E.coli can do that and in fact does this a lot in a commonly used bacterial medium: The popular LB Medium. This is composed of three components: Tryptone, a peptide mix made by digesting milk casein ...
  • 50.5k
3 votes
Accepted

What are mouse LS cells?

Not an easy question, but I got some references about it. Mouse LS cells are Fibroblasts growing in suspension culture, the paper in reference 1 has this paragraph in its Materials and Methods section:...
  • 50.5k
3 votes
Accepted

Soft Agar Substitute

The good news is: You don't need any agar in your plating media, since the bacteria grow on the surface anyway and the plate can take up some additional moisture from your plating media. What I ...
  • 50.5k
3 votes
Accepted

Can you replace glucose with glycerol in cell media?

In most cases, it's not a good idea to replace glucose with glycerol in animal cell media. Animals do possess the ability to metabolize glycerol, via a pathway starting with the enzyme glycerol kinase....

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