Tuberculosis (TB): Progression of the Disease, Latent and Active Infections.

Tuberculosis (TB): Progression of the Disease, Latent and Active Infections.


Tuberculosis, or TB, is one of the oldest
and most common infectious diseases. About one third of the world population is believed
to be infected with TB. Fortunately, only about 5% of these infections progress to active
disease. The other 95% of infected people are said to have a dormant or latent infection;
they do not develop any symptoms, and do not transmit the disease.
Tuberculosis is caused by a rod-shaped bacterium, or a bacillus, called Mycobacterium tuberculosis.
An infection is initiated following inhalation of mycobacteria present in aerosol droplets
discharged into the atmosphere by a person with an active infection. The transmission
process is very efficient as these droplets can persist in the atmosphere for several
hours and the infectious dose is very low – less than 10 bacilli are needed to start
the infection. Once in the lung, the bacteria meet with the
body’s first-line defense – the alveolar macrophages. The bacteria are ingested by
the macrophages but manage to survive inside. Internalization of the bacilli triggers an
inflammatory response that brings other defensive cells to the area. Together, these cells form
a mass of tissue, called a granuloma, characteristic of the disease.
In its early stage, the granuloma has a core of infected macrophages enclosed by other
cells of the immune system. As cellular immunity develops, macrophages loaded with bacteria
are killed, resulting in the formation of the caseous center of the granuloma. The bacteria
become dormant but may remain alive for decades. This enclosed infection is referred to as
latent tuberculosis and may persist throughout a person’s life without causing any symptoms.
The strength of the body’s immune response determines whether an infection is arrested
here or progresses to the next stage. In healthy people, the infection may be stopped permanently
at this point. The granulomas subsequently heal, leaving small calcified lesions. On
the other hand, if the immune system is compromised by immunosuppressive drugs, HIV infections,
malnutrition, aging, or other factors, the bacteria can be re-activated, replicate, escape
from the granuloma and spread to other parts of the lungs causing active pulmonary tuberculosis.
This reactivation may occur months or even years after the initial infection.
In some cases, the bacteria may also spread to other organs of the body via the lymphatic
system or the bloodstream. This widespread form of TB disease, called disseminated TB
or miliary TB, occurs most commonly in the very young, the very old and those with HIV
infections. Tuberculosis is generally treatable with antibiotics.
Several antibiotics are usually prescribed for many months due to the slow growth rate
of the bacteria. It’s very important that the patients complete the course of the treatment
to prevent development of drug-resistant bacteria and re-occurrence of the disease.

So … Sometimes Fireflies Eat Other Fireflies | Deep Look

So … Sometimes Fireflies Eat Other Fireflies | Deep Look


If you think there’s something romantic
about fireflies glowing on a warm summer night… You’d be right. But what you don’t see, is the dark side
of this luminous display. Firefly flashes are a secret code, a language
of light. The light comes from a masterful bit of chemistry. A bioluminescent reaction that generates light
but no heat. So what are they saying? Well, males on the wing are advertising themselves
to females with a bit of sexy skywriting. Take the common Eastern firefly. His signature move? A fishhook-shaped maneuver. Which is why his species is sometimes called
the “Big Dipper.” Her reply is more subtle: a single, slow pulse
from her heart-shaped lantern. Our “Big Dipper” comes bearing a “nuptial
gift,” a present of more than 200 assorted nutrients… kind of like a box of chocolates. Here’s the handoff. Some are lucibufagins — defensive chemicals
fireflies secrete to ward off predators like spiders and birds. These defensive chemicals may help protect
her. Firefly codes are so reliable that anyone
can speak the language. But we’re not the only codebreakers listening
in. Meet Photuris. She’s also a firefly — a larger, stronger
one than the Big Dippers. But she has a weakness. Her species can’t make its own lucibufagins. They have fewer defenses against predators. So she sets a trap to get some. She mimics the glow of other firefly females
— luring in the males of that species. When Mr. Big Dipper shows up with his chemical
gift, she moves in… sucks up those defensive chemicals that she
desperately needs… …then makes a meal of the rest of him. Most fireflies don’t even eat during the
few weeks they spend as adults. But he’s not totally defenseless. If she’s not quick enough, he can secrete
a gooey compound that sticks in her jaw and lets him escape. Another gift from the master chemist. Hey there, it’s Lauren. I know you see that ‘Subscribe’ button there. Here’s what it’ll get you. New Deep Look episodes every two weeks. Keep up with all the weird, gross, and wonderful
things we’re working on. Thanks, and see you soon.