Recent comments in /f/askscience

abat6294 t1_j3archb wrote

Reply to comment by Verneke in How much do water molecules move around within a stationary body of water? by KpgIsKpg

Fun fact. The speed of sound through a substance is dictated by the average speed of the molecules within that substance. Speed of sound in air is about 750mph, so the average speed of each air molecule at any given moment is 750mph.

But they only go extremely short distances before bouncing of another molecule and going another direction.

Edit: The average speed of air molecules is actually closer to 1000mph at room temperature.

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whyyou- t1_j3aqgeu wrote

Reply to comment by whyyou- in Leishmania is a parasite that targets immune cells. Why is it less dangerous than HIV? by robotisland

Leishmania is endemic in some areas but it’s not pandemic due to its need of a vector (the sandfly) that cannot reproduce in some areas.

Why is it easier to treat than HIV?, well the HIV can insert itself into the DNA of its host cell making it extremely difficult to completely eradicate; we can only control the mature viruses but we cannot remove its genetic code from infected cells; as for leishmaniasis, it’s a parasite for wich we have several medications and can be completely eradicated (but it’s not easy, sometimes lengthy IV treatments are needed).

Does the immune system have defenses against Leishmania?? Yes, the infected cells can express some particles in its membrane wich makes them recognizable to the acquired immune system, the infected cells are surrounded by a bunch of other cells causing a “granulomatous inflammation” containing the infection in a single place (most of the times, not always effective) that we can see in the form of skin ulcers or lumps inside the organs (depends of the leishmania type).

Can it be contain by the immune system to a single place? Yes. Can it resolve without treatment? Most likely not.

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whyyou- t1_j3ap4d0 wrote

Reply to Leishmania is a parasite that targets immune cells. Why is it less dangerous than HIV? by robotisland

Leishmania infects a type of cell known as phagocytes, they’re part of the innate immune system and “eat” bacteria, parasites and cellular detritus (very basic functions) meanwhile HIV infects T-CD4 cells wich are part of the acquired immune system and are vital because they act as regulators (akin to an administrator) without them you can have other defensive cells but they won’t do anything; that’s why an advanced HIV infection basically collapses the entire immune system.

As to sexual transmission; the parasite has 2 phases, one is the amastigote wich is replicative and lives within the phagocyte; when the sandfly drinks infected blood it also takes some of these infected cells and inside the insect these amastigotes turn into promastigotes wich are the infectious stage. As you see this bug needs an insect to complete it’s cycle and turn itself infectious so the human / human transmission is very rare, that’s why it’s not considered an STI.

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provocative_bear t1_j3ak0un wrote

Reply to Leishmania is a parasite that targets immune cells. Why is it less dangerous than HIV? by robotisland

Leishmaniasis (called L- from here on out) prevalence largely depends on the prevalence of the sand flies that spread it. While technically it can be spread sexually [1], people with visceral L- are not generally in a condition to be having sex. Therefore, it doesn't spread too well as an STD. Meanwhile, HIV is an insidious disease where the host can survive for years and be active for much of it before succumbing. Additionally, there are often visible signs of L- sores and lesions- while HIV patients show no outward signs of the disease. In short, L- patients are generally clearly sick to both host and partners, while HIV patients are not.

In terms of treatment, you can wipe it out L- with antiparasitics. Treatment is unpleasant, but it is curable. In contrast, HIV is a very sneaky disease. It is a retrovirus, meaning that it can jam its genetic material into your cells' DNA and hide in that form. Even if every virus in the human body is wiped out, the HIV DNA in the host cells can activate, and then the patient is infected all over again. That's why HIV treatments are the way they are, where a patient can be basically normal, but not cured.

[1]: https://pubmed.ncbi.nlm.nih.gov/32943348/

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Aggressive-Visual-44 t1_j3aj5jg wrote

Reply to How does the renal HCO3- reabsorption increase blood pH? by HugoBossPT

Your body secretes H+ and HCO3- through the kidneys. They combine to form H2CO3 (carbonic acid). An enzyme, carbonic anhydrase, splits the carbonic acid into H2O and CO2 in the renal tubular lumen and this water and carbon dioxide enter the renal tubular cell passively. This is because carbon dioxide is lipid soluble and can easily pass through the cell membrane. Water can also move easily across the cell membrane.

Once the H2O and CO2 are inside the renal tubular cell, carbonic anyhydrase acts on them again to form carbonic acid. This carbonic acid splits into H+ and HCO3- again. Now the H+ ion is excreted from the renal tubular cell through a ion exchanger known as the Na-H exchanger where the H+ is exchanged for Na+ in the renal tubular lumen.

Thus, the same H+ ion is used for reabsorption of HCO3- and Na+.

I hope this helps.

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NerdWithoutACause t1_j3airig wrote

Reply to Leishmania is a parasite that targets immune cells. Why is it less dangerous than HIV? by robotisland

HIV is a retrovirus, meaning it inserts its genetic code into the host cells. So not only do those cells make the virus, but all their descendants will, as well. This makes HIV almost impossible to eradicate from the host.

We have drug treatments for leishmaniasis which are extremely effective, and once it’s out of your body, it’s gone for good. With HIV, we have treatments that can inhibit the virus’s spread inside the body, but the infect cells and their progeny are still infected, and will remain so for decades. If the treatment is stopped, the infection will resume in full force.

So basically, leishmaniasis is easily curable in most cases, but HIV is not.

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