Aufbau des Knochens
Das knöcherne Skelett bildet das Stützsystem des Körpers. Es stellt ein großes Mineralreservat (Kalziumionen) dar, dient der Muskulatur als Ansatzfläche und schützt innere Organe. Wie kein anderes Gewebe adaptiert sich der Knochen (Masse und Morphologie) an funktionelle Anforderungen. Er repariert sich selbst, ohne eine “Narbe” zu hinterlassen und kann (bei Kindern) selbst Fehlstellungen nach einem Bruch ausgleichen.
Ever wonder why Spock has green blood? Ask an avid Star Trek fan and they will tell you it’s because his Vulcan haemoglobin, the protein in blood cells that carries oxygen, is based on copper. Human haemoglobin (depicted here in a painting by Irving Geis) is however based on iron. Each haemoglobin molecule is constructed of four identical building blocks made of globin protein (purple) and heme (red). It is the heme group that gives our blood its distinctive red colour. Each heme contains an iron atom surrounded by a ring structure called porphyrin. When porphyrin is bound to iron carrying oxygen, it produces a red colour. While evolution paired up porphyrins with iron in humans, the same is not true for all creatures on earth. Molluscs, like Spock, also use copper giving their porphyrins a green hue.
Written by Lux Fatimathas
THE TIME OF OUR LIVES
Where is the body’s master clock?
The master circadian clock that regulates 24-hour cycles throughout our bodies is found in a region called the suprachiasmatic nuclei (SCN) in the hypothalamus of the brain. The SCN is made up of two tiny clusters of several thousand nerve cells that “tell time” based on external cues, such as light and darkness. The SCN regulates sleep, metabolism, and hormone production.
How important is the SCN? When a rat’s SCN is removed, its daily cycle of activity and sleep is disrupted. The SCN still produces rhythmic chemical signals, even after it has been removed from an animal’s brain.
The SCN is believed to synchronize “local” clocks in organs and tissues throughout the body, either through hormones or changes in body temperature. Gene-operated clocks independent of the brain’s master pacemaker have been found in the liver, lung, testis, connective tissue and muscle.
One example of how a local clock works comes from fruit flies. Cells in their antennae display a circadian rhythm independent of the brain’s master clock. The antennae oscillations correlate with sense of smell, which is more sensitive at night than during the day.
A glucagonoma is a rare tumor of the alpha cells of the pancreas that results in up to a 1000-fold overproduction of the hormone glucagon. Alpha cell tumors are commonly associated with glucagonoma syndrome, though similar symptoms are present in cases of pseudoglucagonoma syndrome in the absence of a glucagon-secreting tumor.
The endocrine system is a complex group of glands that helps to control reproduction, metabolism, growth and development through substances called hormones. It also controls the way you respond to your surroundings and provides the proper amount of energy your body needs to function. Sometimes the glands of the endocrine system are impaired and can cause a hormone imbalance. This hormone imbalance (or endocrine disease/condition) can affect your health in many ways, and some endocrine system diseases/conditions are more serious than others.
Endocrine gland hyposecretion (leading to hormone deficiency)
Endocrine gland hypersecretion (leading to hormone excess)
Tumours (benign or malignant) of endocrine glands
Endocrine disorders are often quite complex, involving a mixed picture of hyposecretion and hypersecretion because of the feedback mechanisms involved in the endocrine system. For example, most forms of hyperthyroidism are associated with an excess of thyroid hormone and a low level of thyroid stimulating hormone.
Thyroid gland. Gamma scan (scintigram) of a healthy human thyroid gland, seen in the profile of a man. The thyroid gland is a main endocrine gland situated at the base of the neck, and is divided into two joined lobes. A radioactive tracer substance shows areas of activity within the gland: green (low activity); red (high). The thyroid produces and stores hormones which control the basal metabolic rate of the body, influence growth and maturation, and regulate blood calcium levels. Gamma scanning involves introducing a radioactive tracer into the bloodstream, which is taken up by certain organs and detected as gamma rays by a gamma camera.
Learning One of Cancer’s Tricks: Chemists Determine One Way Tumors Meet Their Growing Needs
The researchers used chemical tools and molecular modeling techniques developed in their laboratory to determine that GlcNAc inhibits a step in glycolysis (not to be confused with glycosylation), a metabolic pathway that involves 10 enzyme-driven steps. In normal cells, glycolysis is a central process that produces high-energy compounds that the cell needs to do work. But Hsieh-Wilson’s team found that when GlcNAc attaches to the enzyme phosphofructokinase 1 (PFK1), it suppresses glycolysis at an early phase and reroutes the products of previous steps into a different pathway — one that yields the nucleotides a tumor needs to grow, as well as molecules that protect tumor cells. So GlcNAc causes tumor cells to make a trade — they produce fewer high-energy compounds in order to get the products they need to grow and survive.
“We have identified a novel molecular mechanism that cancer cells have co-opted in order to produce intermediates that allow them to grow more rapidly and to help them combat oxidative stress,” says Hsieh-Wilson, who is also an investigator with the Howard Hughes Medical Institute.
How to Become a Neurosurgeon
Becoming a neurosurgeon is one of the most education-intensive career paths that one can choose. On the other hand, it is also one of the most financially rewarding. Neurosurgeons consistently earn the highest salaries among medical professionals owing to the extreme selectivity of training programs (i.e. there are few neurosurgeons with whom to compete), the long and intense training program, and the skill required to actually perform neurosurgery. Neurosurgeons perform surgery on the brain, spinal cord and nerves. Some of the various procedures performed by neurosurgeons are the removal of brain tumors, clipping abnormal blood vessel formations within the brain, and removal of portions of the cerebral cortex to treat epilepsy.
Raising the Alarmin
At the front line of mammalian defence against viruses are special white blood cells known as T-cells. T-cells can seek out and destroy those of our cells that have succumbed to viral infection. Here we see the aftermath of a battle with a viral infection fought on a microscopic scale in mouse spleen cells. An ultra-fine sliver of spleen is shown here with nuclei stained blue (white box, magnified top left, measures 1/200 cm across). Following infection with a virus, some of these spleen cells sent out a chemical distress signal called an alarmin (in this case a specific protein called interleukin-33 shown in green). The signal effectively rallies the troops – a cavalry of protective T-cells (here coloured red) – to prevent the virus from advancing.
Written by John Ankers