Izvrsna stranica

... koju mi je preporučio Krunoslav iz Fizioveta:
http://www.vetscite.org/

Ima jedan vrlo zanimljiv članak o tome kako zapravo pas njuši i vjerujem da bi vas mnoge zanimao pa ga pejstam ovdje. Obratite pažnju na zanimljiv zadnji pasus, meni je to vrlo novo i vrlo zanimljivo:

The secret of a dog's sniffer

After a massive earthquake struck the Sichuan Province of China last year, troops and rescue workers brought in dogs to sift through the rubble. With a scent sensitivity many thousands of times greater than our own, the canines located numerous survivors--even those buried under thick debris for days. Now researchers think that they have figured out a key reason why dogs are such superior sniffers. The study could be useful in building odor-sensitive, artificial-nose machines. Scientists have known since the 1950s that dogs and other keen-scented mammals such as rats and rabbits have a specialized anatomical structure in their nasal cavity. Called the olfactory recess, it's a large maze of highly convoluted airways that humans and all other primates lack. In dogs, the recess lies right behind the eyes and takes up almost half of the interior of the nose. Scientists knew that something about the structure allows dogs to sniff odors invisible to humans. "But no one had looked at how air and odors actually flow inside" a dog's nose to reach that recess, says Brent Craven, a mechanical engineer at Pennsylvania State University, University Park.

So Craven and his colleagues created a computer model of a canine nose. First, they scanned the nasal airway of a mixed-breed cadaver with high-resolution magnetic resonance imaging. "We then had to make our model simulate how dogs sniff," says Craven. But because that skill had also never been studied (although it has been in humans and rats), the researchers outfitted seven dogs, including a Pomeranian and a Labrador retriever, with a special muzzle. The device measured their rate of sniffing as they smelled things such as spoonfuls of peanut butter and tuna. Despite the wide range of sizes and weights, "all the dogs sniffed at about the same frequency, five times per second," says Craven. That's the same rate at which they pant. But "we knew they were sniffing and not simply breathing," says Craven, because high-speed videos showed "their nostrils flaring, which happens when they're sniffing, not when they're breathing." The team also mapped the flow of air into the dogs' noses as they sniffed, enabling them to calculate the nostrils' aerodynamic reach.

When the computer nose started sniffing, it picked up some surprising results. "First, the simulation showed that when a dog sniffs, each nostril pulls in a separate odor sample," says Craven. Via its olfactory sensors, "the dog can tell which nostril is pulling in the scent," so it knows which direction to go when tracking. Further, the researchers report today in the Journal of the Royal Society Interface, a dog's nose has a unique nasal airflow pattern, which helps transport odor molecules quickly via a single airway to the olfactory recess. Here, the smell is retained in the maze of scent receptors even after the dog exhales; the odor is not expelled as it is with humans. It's "very similar" to a rat's airway, says Craven, who expects that this pattern will be found in any mammal with a keen sense of smell.

ScienceNow
January 12, 2010

i s iste stranice još jedan zanimljiv članak o povezanosti opsesivno kompulzivnih poremećaja s određenim genom:

Sniffing out clues to dogs' compulsive behavior

By Nicole Davis New research on Doberman pinschers reveals a gene involved in compulsive behavior that could help scientists understand compulsive disorders in humans. At first glance, a dog chasing its tail seems a harmless, if fruitless, pursuit. But for many dogs and their owners, the habit has a dark side, one that means endless hours and energy spent on the same task, to the exclusion of nearly all others. The cause, a type of compulsive disorder, can result in lack of sleep and even physical injury. "It really is a hindrance for other normal activity and it often doesn't stop at bodily harm," said Kerstin Lindblad-Toh, Scientific Director of Vertebrate Genome Biology at the Broad Institute and professor at Uppsala University, Sweden. "So it's clearly not a good thing for the dog." In dogs, such compulsive behaviors tend to run in certain breeds, and specific breeds exhibit characteristic behaviors. For example, Doberman pinchers usually lick or suck their flanks, often to the point of bleeding and skin infections. Other dog breeds, such as bull terriers, repeatedly chase their tails.

But there is a common thread. "They are all behaviors that are normal," said Elinor Karlsson, a postdoctoral researcher at the Broad Institute, "but they are being done way too much," and often to dogs' detriment. Moreover, such compulsive behaviors — known as canine compulsive disorder (CCD) — show some remarkable similarities to a human behavioral disorder called obsessive-compulsive disorder. So, a deeper understanding of the genetic basis of the disorder in dogs could lead to a clearer picture of the condition in both species. Now, Lindblad-Toh, Karlsson and their colleagues, including Nicholas Dodman at Tufts University and Edward Ginns at the University of Massachusetts Medical School, have taken a first step toward that goal, identifying a gene associated with CCD. The work was published online December 22 in the journal Molecular Psychiatry. The researchers explored the genetic basis of CCD by focusing on the Doberman pincher breed. The manifestations of CCD, including flank sucking, are not only common in the breed, but they are also easily distinguishable: dogs either do it or they don't. That facilitated the researchers' task of identifying affected dogs, making it possible to collect a sufficient number of DNA samples for study.

With roughly 150 affected and unaffected dogs, the researchers analyzed the DNA samples using a technique known as genome-wide association, which scans thousands of genetic markers — called SNPs or single nucleotide polymorphisms — throughout the genome to identify ones that are more common in affected dogs compared to in unaffected ones. Those high frequency markers act as signposts for genes and other key functional genomic elements that increase a dog's risk of developing the disorder. "The nice thing is that we had one extremely strong peak and there's only one gene in that entire region...and our SNP sits right in the middle of that one gene," said Karlsson, a co-author of the Molecular Psychiatry paper. The gene in question is called CDH2. Relatively little is known about how it works because the gene plays an important role early in embryonic development, which has made it difficult for scientists to learn about its functions later in life through studies of animal models. What is known is that the gene is part of a large family of genes known as cadherins, and this particular cadherin appears to act in the brain, specifically at the junctions between neurons known as synapses. While the new data implicates a gene that acts in the right place to influence behavior, the researchers acknowledge there is still much work left to be done, both in extending their work in dogs and in beginning to apply it to humans. Nevertheless, there is hope that such efforts will lead to an enhanced understanding of behavioral disorders in both species.

PhysOrg.com
January 12, 2010

Na jednoj drugoj stranici pronašla sam dosta zanimljivu tabelu sa razlikama u tzv. kompleksu mirisa na žive i mrtve osobe. Kako nisam na tako nešto još nigdje naišla, ovo je dosta interesantno.
Text je napisao Nizozemac Jan Bogers. Cijeli se nalazi na ovoj stranici: http://www.sardogs.nl/literatuur/sardus.html

Živa osoba (tabela imenovana kasnije kao 4)
Before we give the tables with the scent complexes, we will start by stating some facts about a living victim. Substances which on the body of a living victim are heated depending on the temperature of the body. The temperature on the outside of a living body is constant and ± 270 C. Due to this body temperature the victim will constantly generate a particular biological scent. At this temperature certain substances on the body will vaporize and others will not. Of course volatile substances vaporize sooner that non volatile substances. Also belonging to this temperature there is a particular bacterial metabolism on the skin of the victim.
Last but not least a living person is breathing and sweating.
We only give the categories I and II as these are of major importance and categories III and IV are the same for both living and dead victims under the condition that they are located in a similar situation.

SCENT COMPLEX	I Biological scents from victim	II Attached to the skin of victim
More volatile substances	Sweat, breath, vaporizing urine, bacterial metabolism!	Perfume, strong vaporizing shampoo, chemical substances that are on the victim and that vaporize because of the body temperature.
Less volatile substances	Fatty acids (skin fat), saliva (spit), skin pieces, dandruff, hair, nails	Soap, other less volatile, chemical substances that are on the victim

Osoba mrtva 3 dana (tabela imenovana kasnije kao 5):
Turning to the discussion of the scent complex produced by a dead victim we see immediately that there is one very important difference between a dead and a living victim: A dead victim is not breathing nor sweating!
If the outside temperature is lower than 270 then the temperature of the dead body is decreasing at a constant rate of about 0.5 degree C per hour (of course this strongly depends on outside temperatures!). Due to this temperature change, the victim will generate a changing scent complex until a stable temperature is reached. This is the temperature of the surroundings. At this temperature fewer substances on the body will vaporize.
After two days the destruction process of a dead person starts. Again this depends strongly on the outside conditions such as temperature, humidity, etc. In this process bacteria and insects play an important role. There will be a different bacterial metabolism on the victim compared with the bacterial metabolism on a living victim. Anal gases are produced.
If the outside temperature is higher than 270 then the process of destruction will start almost directly again causing the scent complex to change rapidly!
Of course during the process of destruction the scent complex does not remain the same. It will undergo some major changes in time. However to clarify our major point of discussion it is sufficient to restrict ourselves to the facts stated above. For more detailed discussion see N. Sharp [4].
Again we restrict ourselves to categories I and II.

SCENT COMPLEX	I Biological scents from victim	II Attached to victim
More volatile substances	Anal gases, Bacterial metabolism of destruction. Scents produced by insect metabolism.	More volatile, chemical substances that are on the victim.
Less volatile substances	fatty acids (skin fat), skin pieces, dandruff, hair, nails	Less volatile, chemical substances that are on the victim.

Of course as the scent complex follows a trajectory from table 4 to table 5 from the moment of death to three days after death. But one thing is directly discriminating between tables 4 and 5 and that is the fact that at moment of death breathing stops and sweat production stops!
Analysis problem 3. Returning now to our problem 3 of Section 4 it will be clear that a dog trained for water search (searching dead persons) and for rubble search (searching living persons) should be trained during the rubble training on breath, sweat vapor and bacterial metabolism produced by living victims in the rubble. Also this dog should be regularly tested and corrected if it gives false alerts on fatty acids coming from clothing and recently used beds. This requires special attention. The following questions often arise after the previous discussion.

Question 1. Is it possible to train a dog on the search for dead persons and not give false alerts on recently used beds and clothing?
Answer. In order to give an answer to this question we must look at table 5 in order to find those scents coming from a dead victim that are not on clothing and beds. This leads us to the conclusion that training on the scents produced by bacterial or insect metabolism is a possibility. Another possibility is training the dog on anal gases. However the production of these gases stops after a period of time.

Question 2. Is it possible that a dog that is trained to search for living persons gives alerts on dead victims whereas it is trained to give no alerts on clothes, beds and other objects carrying human scents?
Answer. In order to give an answer to this question we must look at tables 4 and 5 in order to find those scents coming from a living and a dead victim that are not on clothing and beds. We see that if the victim has died recently, then the bacterial metabolism has not yet radically changed. We already stated that the change in the scent complex follows a trajectory from table 4 to table 5 from the moment of death to three days after death. If the dog has picked the scent produced by the bacterial metabolism out of the complex itself or when it is trained to work on this scent, then it is possible that he gives alerts on recently died victims still producing this scent. This leads us to the conclusion that training on sweat vapor and breath does not exclude this possibility. The only way to be absolutely certain that this will not happen is to test the dog to make a selection between a living victim and human tissue! This human tissue should be of a varying age.

CONCLUSIONS
It is my opinion that this theory is not a final stage. However during the years I have been training search and rescue dogs I noticed that in contrast with other disciplines of search dogs such as drugs or explosives the rescue dog handlers do not always realize on what scent complex they actually train their dog! This can cause serious problems such as false alerts in a disaster area. As rescue dog handlers often have to make decisions with great responsibility and it is of major importance that they realize exactly for what kind of work their dog is trained for! Consequently we come to the following conclusions.

-It has strong preference to train a SAR dog for a specific task, with its specific scent or scent complex, and not for a large scale of tasks! This will avoid unnecessary confusion and problems.

-If a SAR dog is trained for more disciplines with a possibility of confusion then we have to pay much attention to this problem in the training of this dog!

-If a SAR dog is trained for a specific task it should not be used for tasks it is not trained and tested for! If the authorities call for help the dog handlers should inform these authorities about the work the dogs have been trained for and can reliably perform!

-SAR dogs trained to search for living victims should be trained with living victims only! Furthermore they should be tested regularly if they do not give false alerts on object carrying human scents.

-SAR dogs trained to search for dead victims should be trained on human tissue only! Also these dogs should be tested if they do not give false alerts on object carrying human scents.

Hvala Mirela, ovaj članak mi je bio jako interesantan

Anaaa wrote:

Hvala Mirela, ovaj članak mi je bio jako interesantan

molim :-)

nadam se da još netko čita sve ove stvari da znam da mi trud nije uzaludan :-)

vrlo zanimljivo, pogotovo onaj dio o tome kako pas koji trazi zive, mora biti treniran za trazenje samo zivih, i ne smije reagirati na stvari koje imaju ljudski miris a nisu zivi ljudi....

Bruna wrote:

vrlo zanimljivo, pogotovo onaj dio o tome kako pas koji trazi zive, mora biti treniran za trazenje samo zivih, i ne smije reagirati na stvari koje imaju ljudski miris a nisu zivi ljudi....

elena wrote:

Bacila sam oko i bas je interesantno. Morat cumalo bolje to proucit za vikend!

Ja se isto spremam malo to proučiti za vikend...