Arxiu d'etiquetes: cannibalism

Prions: special proteins

Do you remember mad cow disease? Some years ago it caused media hype because this illness, which affected animals, affected people too. Then, it was discovered that prions were the cause. So, I will discuss what prions are and the diseases that they produce.

WHAT ARE PRIONS?

Prions are proteins, but with different characteristics. Proteins are molecules formed by amino acids, which are bound by peptide bonds. All proteins are composed by carbon, hydrogen, oxygen and nitrogen. They are localized in all cells of the body and they participate in all biological processes that are produced. While DNA carries genetic information of the cell, proteins execute the work led by this information.

Proteins are the most varied macromolecules. In each cell there are miles of different proteins, with an extended range of functions. Between them: to be structural components of cells and tissues, to act in the transport and storage of little molecules, to transmit information between cells and to proportionate a defence in front of an infection. However, the main function is to act as enzymes, which catalyse most of chemical reactions in biological systems.

Prions are proteins with pathogenic and infectious characteristics (Video 1). They are not virus nor alive organisms; they are proteins without nucleic acid, it means, without DNA. They are localized in the surface of the central nervous system, especially in neurons; although they are also located in other body tissues of adult animals. Significant levels have been detected in the heart and skeletal muscle, and to a lesser extent in other organs except the liver and pancreas.

Video 1. What are prions? (Source: YouTube)

THE CELLULAR PRION PROTEIN

There is a change in the configuration of the cellular prion protein PrPc (Figure 1) in the diseases caused by prions. This protein has a protector role for cells and helps them respond in front of lack oxygen. The consequence of prions on this protein is the alteration of its functionality, producing a protein PrPSc with altered configuration. However, both configurations have the same sequence of amino acids. The secret of the different behaviour is the wrong folding, it means, the wrong conformation.

prpc prpsc
Figure 1. Left: normal protein (PrPc). Right: protein with altered configuration (PrPSc)(Source: Searching for the Mind with Jon Lieff, M. D.)

PRION DISEASES

Prion diseases are neurodegenerative processes produced by abnormal metabolism of a prion protein. These affect humans and animals and have a fatal clinical evolution, with the death as final.

There are various prion diseases, however, symptoms and clinical features are shared (Table 1). Some of these clinical features are dementia, ataxia (discoordination in the movement of body), insomnia, paraplegia and abnormal behaviors. The brain acquires a spongiform aspect, it means, an aspect like a sponge. This is due to accumulation of prion proteins in neurons, where amyloid plaques are formed.

Amyloid plaques are caused by accumulation of amyloid peptide, an essential protein for cellular function of the body. This accumulation in the brain can generate toxicity for nervous cells.

Until today there is any treatment to cure, improve or control symptoms and signs of these diseases.

Tabla 1. Prion diseases and its clinical features (Source: Rubio, T. & Verdecia, M. Enfermedades priónicas. MEDISAN 2009; 13(1))

DISEASE SYMPTOMS AGE DURATION
Creutzfeldt-Jakob

Dementia

Ataxia

< 60 years

1 month – 10 years

(average 1 year)

Kuru

Ataxia

Dementia

40 years (29-60) 3 month – 1 year
Fatal familial insomnia

Insomnia

No autonomy

Ataxia

Dementia

45 years (35-55) 1 year

CREUTZFELDT-JAKOB SYNDROME

During 18th century, European farmers described a neurodegenerative disease that affected sheep and goats, called scrapie. The affected animals will compulsively scrape off their fleeces against rocks, trees, or fences. Furthermore, its brain looked like a sponge. So, this is the birth of the word spongiform.

However, until 20th century, in 1920, neurologists Creutzfeldt and Jakob described the first cases of spongiform encephalopathy in humans (Figure 2) and called the disease with their names.

creutzfeldt-jakob-disease-cjd.jpg
Figure 2. Comparison of two brains: a brain affected by Creutzfeldt-Jakob disease (left) and a healthy brain (right) (Source: Health & Medical Information)

In this disease, there is a loss of memory, lack coordination and damage of mental abilities. The balance problems are common and, sometimes, are manifested in the beginning. Many patients lose autonomy and are unable to take care of themselves in later stages of the disease.

Due to prion nature of the disease, any symptom is possible and it depends on the area of the brain that is being affected.

KURU

It is a rare disease, localized in New Guinea. The main risk factor to suffer the disease is the intake of brain human tissue, which can contain infectious particles.

It is the reason that it is associated with people who practice a form of cannibalism, in which the brains of dead people are eaten as part of a funeral ritual. Although this practice ended in 1960, cases of kuru have been reported years later.

FATAL FAMILIAL INSOMNIA

It is a familial and inherited disease, which people affected suffer progressive insomnia. The human brain needs to sleep and rest, so permanent insomnia (there is not treatment with drugs) causes the death of patients.

Insomnia is due to a permanent and irreversible alteration of the sleep-wake cycle, which is characterized by the inability of the patient to develop REM and non-REM sleep.

REFERENCES

  • Alberts, B. et al. (2016). Biología molecular de la célula. Barcelona: Omega.
  • Rubio, T. & Verdecia, M. Enfermedades priónicas. MEDISAN 2009; 13(1)
  • Wemheuer, W. M. et al. Similarities between Forms of Sheep Scrapie and Creutzfeldt-Jakob Disease Are Encoded by Distinct Prion Types. Am J Pathol. 2009; 175(6): 2566–2573
  • Manual MSD
  • Early Clinical Trial
  • MedlinePlus
  • Main picture: Canal44

MireiaRamos-angles

Symbiosis: relationships between living beings

Predation, parasitism, competition… all living beings, besides interacting with the environment, we relate to other living beings. What types of relationships in addition to those you know? Do you feel like to know them?

INTRODUCTION

The group of all living beings in an ecosystem is called biocenosis or community. The biocenosis is formed in turn by different populations, which would be the set of individuals of the same species occupying an area. For survival, it is imperative that relations between them are established, sometimes beneficial and sometimes harmful.

INTERESPECIFIC RELATIONSHIPS

They are those that occur between individuals of different species. This interaction it is called symbiosis. Symbiotic relationships can be beneficial to a species, both, or harmful to one of the two.

Detrimental to all the species involved:

Competition: occurs when one or more resources are limiting (food, land, light, soil …). This relationship is very important in evolution, as it allows natural selection acts by promoting the survival and reproduction of the most successful species according to their physiology, behavior …

Las selvas son un claro ejemplo de competencia de los vegetales en busca de la luz. Selva de Kuranda, Australia. Foto de Mireia Querol
Rainforests are a clear example of competition between vegetals in the search for light. Kuranda rainforest, Australia. Photo by Mireia Querol
One species has benefits and the other is detrimented:
  • Predation: occurs when one species (predator) feeds on another (prey). This is the case of cats, wolves, sharks
foca, león marino,
Great white shark (Carcharodon carcharias) jumping to depretade a marine mamal, maybe a sea lion. Photo taken from HQ images.
  • Parasitism: one species (parasite) lives at the expense of other (host) and causes it injury. Fleas, ticks, pathogenic bacteria are the best known, but there are also vertebrate parasites, like the cuckoo that lay their eggs in the nests of other birds, which will raise their chicks (brood parasitism). Especially interesting are the “zombie parasites”, which modify the behavior of the host. Read this post to learn more!
    Carricero (Acrocephalus scirpaceus) alimentando una cría de cuco (Cuculus canorus). Foto de Harald Olsen
    Reed warbler (Acrocephalus scirpaceus) feeding a cuckoo’s chick (Cuculus canorus). Photo by Harald Olsen

    Parasites that live inside the host’s body are called endoparasites (such as tapeworms), and those who live outside ectoparasites (lice). Parasitism is considered a special type of predation, where predator is smaller than prey, although in most cases does not cause the death of the host. When a parasite causes illness or death of the host, it is called pathogen.

    Cymothoa exigua es un parásito que acaba sustituyendo la lengua de los peces por su propio cuerpo. Foto de Marcello Di Francesco.
    Cymothoa exigua is a parasite that replaces the tongue of fish with their own body. Picture by Marcello Di Francesco.

Kleptoparasitism is stealing food that other species has caught, harvested or prepared. This is the case of some raptors, whose name literally means “thief.” See in this video a case of kleptoparasitism on an owl:


Kleptoparasitism can also occur between individuals of the same species.

One species has benefits and the other is not affected:
  • Commensalism: one species (commensal) uses the remains of food from another species, which does not benefit or harm. This is the case of bearded vultures. It is also commensalism the use as transportation from one species over another (phoresy), as barnacles attached to the body of whales. The inquilinism is a type of commensalism in which a species lives in or on another. This would apply to the woodpeckers and squirrels that nest in trees or barnacles living above mussels. Finally, metabiosis is the use of the remains of a species for protection (like hermit crabs) or to use them as tools.
    El pinzón carpintero (Camarhynchus pallidus) utiliza espinas de cactus o pequeñas ramas para extraer invertebrados de los árboles. Foto de
    The woodpecker finch (Camarhynchus pallidus) uses cactus spines or small branches to remove invertebrates from the trees. Picture by Dusan Brinkhuizen.
    Both species have benefits:
  • Mutualism: the two species cooperate or are benefited. This is the case of pollinating insects, which get nectar from the flower and the plant is pollinated. Clownfish and anemones would be another typical example, where clown fish gets protection and food scraps while keeps predators away and clean parasites of the sea anemonae. Mutualism can be optional (a species do not need each other to survive) or forced (the species can not live separately). This is the case of mycorrhizae, an association of fungi and roots of certain plants, lichens (mutualism of fungus and algae), leafcutter ants

    Las hormigas Atta y Acromyrmex (hormigas cortadoras de hogas) establecen mutualismo con un hongo (Leucocoprinus gongylophorus), en las que recolectan hojas para proporcionarle nutrientes, y ellas se alimentan de él. Se trata de un mutualismo obligado. Foto tomada de Ants kalytta.
    Atta and Acromyrmex ants (leafcutter ants) establish mutualism with a fungus (Leucocoprinus gongylophorus), in which they gather leaves to provide nutrients to the fungus, and they feed on it. It is an obligate mutualism. Photo taken from Ants kalytta.

INTRAESPECIFIC RELATIONSHIPS

They are those that occur between individuals of the same species. They are most beneficial or collaborative:

  • Familiars: grouped individuals have some sort of relationship. Some examples of species we have discussed in the blog are elephants, some primates, many birds, cetaceans In such relationships there are different types of families.
  • Gregariousness: groups are usually of many unrelated individuals over a permanent period or seasonal time. The most typical examples would be the flocks of migratory birds, migration of the monarch butterfly, herds of large herbivores like wildebeest, shoal of fish

    El gregarismo de estas cebras, junto con su pelaje, les permite confundir a los depredadores. Foto tomada de Telegraph
    Gregariousness of these zebras, along with their fur, allow them to confuse predators. Photo taken from Telegraph
  • Colonies: groups of individuals that have been reproduced asexually and share common structures. The best known case is coral, which is sometimes referred to as the world’s largest living being (Australian Great Barrier Reef), but is actually a colony of polyps (and its calcareous skeletons), not single individual.
  • Society: they are individuals who live together in an organized and hierarchical manner, where there is a division of tasks and they are usually physically different from each other according to their function in society. Typical examples are social insects such as ants, bees, termites

Intraspecific relations of competition are:

  • Territorialityconfrontation or competition for access to the territory, light, females, food can cause direct clashes, as in the case of deer, and/or develop other strategies, such as marking odor (cats, bears), vocalization

    Tigres peleando por el territorio. Captura de vídeo de John Varty
    Tiger figthing for territory. Video caption by John Varty
  • Cannibalism: predation of one individual over another of the same species.

And you, as a human, have you ever thought how do you relate with individuals of your species and other species?

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

REFERENCES

You are a bit Neanderthal

Neanderthals are perhaps the better known ancestor for the general public, as like as Australopithecus afarensis (Lucy). The classical view of them, a rough, coarse, crude, unintelligent beings, is still alive in the popular imagination (even “Neanderthal” is used as an insult), but in recent years the research tells us they were not like this. Discover in this article who they were and why you’re a bit Neanderthal.

WHAT WAS A NEANDERTHAL LIKE?

Homo neanderthalensis was the first hominin fossil discovered and currently we have hundreds of fossil specimens of all ages, so is the best known fossil hominin. Got its name from the Neander Valley (Neanderthal in German), a valley near Düsseldorf.

distribución geográfica neandertal
Geographical distribution of the Neanderthals. Image by Ryulong

They lived in Europe (including Siberia) and southwestern Asia,  350,000-28,000 years ago (40,000 according to some sources), an era marked by glacial cycles. They existed in the world longer than us, Homo sapiens.

Neanderthals had various adaptations to cold, as robustness and less height than H. sapiens, and a wide nasal cavity.

Comparación del cráneo de sapiens i neanderthalensis. Cleveland Museum of Natural History. Foto de Matt Celeskey.
Skull comparison between sapiens and neanderthalensis. Cleveland Museum of Natural History. Photo by Matt Celeskey.

Skull highlights its size, with an average capacity of 1,475 cm3, somewhat higher than the modern human skull, and is more elongated backwards (protrusion or occipital bun). Also it is observed easily a powerful supraorbital torus (bone above the eye sockets). Their pelvis was wider than ours and had shorter legs.

homo neanderthalensis, hombre de neandertal, neanderthal, american museum of natural history, amnh
Recreation of a skeleton of H. neanderthalensis. American Museum of Natural History. Photo by Mireia Querol

HOW THEY LIVED?

FEEDING

Neanderthals were skilled and selective hunters, they faced large animals (as witnessed from their injuries, some fatal) and used hunting strategies like the populations of Homo sapiens that arrived in Europe after them. They were seasonal hunters due to seasonal climate (basically reindeer in winter, deer and wild boar in summer). So their diet was based on meat, but near the coast also ate molluscs such as mussels, which were boiled to open them. It is likely that practiced cannibalism. Also captured marine mammals such as monk seals and dolphins stranded, and also ate cooked cereals.

UTENSILS

Homo neanderthalensis had a lithic industry (stone work for constructing tools) called Mousterian, also associated with other species such as H. heidelbergensis and Homo sapiens that requires great skill and planning. In some deposits it has been found composite tools using adhesives.

Neandertal con ornamentación de plumas. Reconstrucción de Fabio Fogliazza.
Neanderthal with feather ornamentation. Reconstruction by Fabio Fogliazza.

There are no remains of clothes, but is likely that they used fur to cover them given the climatic changes that they faced.

In Spanish caves perforated shells were found with traces of pigments, suggesting that they were used as dishes for body painting or dyeing fur. It is suggested that perhaps they were the first to make cave paintings, contrary to the belief that we are the only ones who did it. They also carved bone and used feathers as personal decoration. All this suggests some sort of symbolic thought, associated until recently as an exclusive feature of Homo sapiens.

pintura rupestre, manos, arte rupestre, pinturas rupestres más antiguas, pinturas neandertales
Cave paintings of hands (“Groups of hands”) and red disks in El Castillo cave, Spain. They are the oldest in Europe (41,000 years) and maybe Neanderthals painted it, rather than sapiens as previously thought. Photo: Science.

SOCIETY

Neanderthals are believed that lived in family groups, although recent studies suggest that females would move to other families when they reached adulthood, while adult men remained with the original family.

entierro, neandertal, neanderthal, compasion, autoconciencia
Neanderthal showing compassion to a dead partner. Recreations by Elisabeth Daynès, CosmoCaixa Barcelona. Photo by Mireia Querol

One of the most important features of the Neanderthals is that they were probably the first human ancestors that buried their dead, which shows an awareness of the individual self and their peers, plus some symbolic or abstract thought as mentioned above. This increased the survival of individuals and made stronger social bonds, and also helped other dependent people such as elderly and sick fellows (as the old man from La Chapelle-aux-Saints). Their life expectancy was about 40 years.

DID THE NEANDERTHALS TALK?

Another unanswered question, though are reaching strength opinions of some scientists as Juan Luis Arsuaga, thanks to the remains of the site with more fossils of Homo in the world, La Sima de los Huesos (Burgos). Neandedrthals could have an oral language, against the widespread thinking so far that they had a communication based in grunts. In addition to the anatomical language adaptations, the Neanderthal DNA contains the FoxP2 gene, related to speech in H. sapiens.

neanderthal
Recreation of a Neanderthal camp. Neanderthal Museum in Krapina, Croatia.

NEANDERTHAL EXTINCTION

The extinction of Neanderthals is one of the most controversial debates in paleoanthropology. They disappeared 28,000 years ago, after the arrival of anatomically modern humans in Europe about 60,000 years ago. A time ago extinction was associated with their lower intellectual capacity, but we have seen that did not have to be this way, since they were much like us. Inability to adapt to climate changes? Less reproductive capacity? More infant mortality? Less efficiency for resources or hunting? Direct wars? Imported diseases? Or … maybe sex?

HYBRIDIZATION BETWEEN H. SAPIENS  AND H. NEANDERTHALENSIS

Refused for a long time, we now know that our species reproduced with Neanderthals when they were about to be genetically incompatible (100,000 years ago), because they coexisted between 2,600 and 5,400 years ago and left fertile offspring. So much so, that the Neanderthal genome accumulated by all living human beings is 20%, although the percentage in an individual -without african roots-  is from 1 to 3%.

In June 22nd was published in Nature the discovery of a jaw in Romania of an anatomically modern Homo sapiens (40,000 years old) containing between 6 and 9% of Neanderthal DNA, which implies that their neanderthalensis ancestry was only 4 or 6 generations back in his pedigree.

pelirrojo, redhead, neanderthal
Redhead Homo sapiens and recreation of H. neanderthalensis. Photo by Science

So another possible explanation for their extinction is due to these reproductive crossings. Homo sapiens were more numerous, which could have caused that the Neanderthal genes were diluted” over thousands of generations. This is known as extermination by hybridization.

WHAT IMPLICATIONS WE HAVE BEING A BIT NEANDERTHALS?

It is believed that Neanderthals genes brought us some advantages, as some characteristics of the skin and hair, such as color and thickness, which could help our species to colonize cooler areas. In fact some Neanderthals could be light-skinned and redheads.

But some diseases can be associated to that heritage: increased risk of biliary cirrhosis, lupus, diabetes, Crohn’s disease and even difficulty in quitting smoking (smokers: not worth using it as an excuse).

In short, it is exciting to think that we lived and even mated with a species so similar to ours and that somehow, still exist in each of us. We may not be as special as we thought.

Currently we are the only representatives of the genus Homo, but in ancient times it was not. Can you imagine a world where you would meet  a Neanderthal  in the street and tell them good morning”?

 

neanderthal, suit, traje, camisa, nenadertal
Neanderthal in suit. Photo: Neanderthal Museum/H. Neumann

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY