Unless you were born blind you already know how valuable your eyes and vision are in coping with life. Helping us to process information on the world around us, our eyes constantly work to help us enjoy life and avoid danger.
Dogs also use their eyes in similar ways but with a few minor important differences. We see far and near fine detail in a wide range of colors and shades. Dogs however, even sight hounds which have good vision, have a poorer color range and they are much better at detecting movement rather than detail. This gives them an advantage with night vision but they are poorer at seeing fine or close detail. The main advantage dogs have is that they don’t have to rely purely on vision for information on their world. An acute sense of smell and excellent hearing, along with good motion sensing vision, mean that dogs sense much more of their surrounds than mere humans. This extended sensory ability made them ideal companions to early man when danger lurked around every corner.
Dogs eyes even look remarkably similar to human eyes. Like us, dogs have a range of eye colors although their predominant color is brown. One important difference between us is that dogs have a third eyelid called a nictitating membrane. Although this membrane is not easily seen, certain diseases and eye irritation can make it stand out. The third eyelid sits in the inside corner of a dogs eye and helps to protect it from irritation by cleansing and lubricating the eye.
Most of the eye diseases and problems seen in dogs are the same as those found in humans. One of the most common problems seen in dogs is due to simple eye irritation. The same environmental irritants that afflict us afflict our dogs. Dust, smoke and chemical pollution are the commonest cause of watery irritable eyes in our favorite pets. Apart from seeing red, teary eyes which are often swollen, you will likely observe your dog rubbing or scratching at their eyes. Look carefully at whether both or only one eye is irritated. Symptoms occurring in only one eye usually mean a foreign body or injury in the eye involved.
Blocked tear ducts can also produce excessively watery eyes in dogs as well as humans. In some dog breeds, such as older Poodles and Shih Tzu’s, you will often see damp matted fur around their eyes that signals tear duct blockages. An expert opinion from a vet is often needed to tell the difference between the different causes of watery eyes.
Another trait that elderly dogs share with elderly humans is the development of cataracts. Most long term dog owners have seen the cloudy milky haze that spreads in the centre of each pupil as the cataracts form. This milky haze is the lens inside your dogs eye becoming opaque and the dog slowly becomes blind. It’s important to distinguish cataract from another change called Lenticular Sclerosis. Lenticular Sclerosis is a condition which looks similar to cataract but where the only the center of the dogs lens hardens and vision remains unaffected. Both problems are seen in elderly dogs.
Showing posts with label humans. Show all posts
Showing posts with label humans. Show all posts
Dog Genome May Shed Light On Human Disease
Scientists have succeeded in sequencing the dog genome, an accomplishment that could lead to better health for humans as well as canines. An international team of researchers have published their detailed analysis in the journal Nature.
“Of the more than 5,500 mammals living today, dogs are arguably the most remarkable,” says senior author Eric Lander, PhD, director of the Broad Institute at of MIT and Harvard. He is a professor of biology at MIT and systems biology at Harvard Medical School, as well as a member of the Whitehead Institute for Biomedical Research.
“The incredible physical and behavioral diversity of dogs — from Chihuahuas to Great Danes — is encoded in their genomes. It can uniquely help us understand embryonic development, neurobiology, human disease and the basis of evolution,” Dr. Lander notes.
Powerful Tool
“When compared with the genomes of human and other important organisms, the dog genome provides a powerful tool for identifying genetic factors that contribute to human health and disease,” says Francis S. Collins, MD, PhD, director of the National Human Genome Research Institute (NHGRI), which supported the research.
“This milestone is especially gratifying because it will also directly benefit veterinary researchers’ efforts to better understand and treat diseases afflicting our loyal canine companions,” Dr. Collins adds.
Humans domesticated the dog, Canis familiaris, from gray wolves as long as 100,000 years ago. As a result of selective breeding over the past few centuries, modern dog breeds present a model of diversity. From six-pound Chihuahuas to 120-pound Great Danes, from high-energy Jack Russell Terriers to mild-mannered basset hounds, and from Shetland sheepdogs with their herding instincts to pointers inclined to point, humans have bred dogs for desirable physical and behavioral traits.
Such breeding practices preserve preferred traits of one generation in the next, but they also predispose many dog breeds to genetic disorders, including heart disease, cancer, blindness, cataracts, epilepsy, hip dysplasia and deafness.
The research group found that while different breeds show amazing physical diversity, they often share large segments of their DNA, likely reflecting their recent shared origin. As a result, genetic tools being developed at the Broad Institute and NHGRI for any one breed of dog are likely to be useful in genetic experiments in nearly any breed.
Evolutionary Tree
While dogs occupy a special place in human hearts, they also sit at a key branch point, relative to humans, in the evolutionary tree. It was already known that humans share more of their ancestral DNA with dogs than with mice. The availability of the dog genome sequence has allowed researchers to describe a common set of genetic elements — representing about 5 percent of the human genome — that are preferentially preserved among human, dog and mouse.
Rather than being evenly distributed, some of these elements are crowded around just a small fraction of the genes in the genome. Future studies of these clusters may give scientists the critical insight needed to unravel how genomes work.
Elaine A. Ostrander, PhD, chief of NHGRI’s Cancer Genetics Branch, is a co-author of the Nature paper, along with postdoctoral research fellows, Heidi G. Parker and Nate B. Sutter. In addition, Dr. Ostrander is the lead author of the white paper that sets forth the biomedical rationale for sequencing the dog genome.
Dr. Ostrander’s laboratory maps genes responsible for susceptibility to cancer — including breast and prostate cancers — in canines and humans.
“The leading causes of death in dogs are a variety of cancers, and many of them are very similar biologically to human cancers.” says Dr. Ostrander. “Using the dog genome sequence in combination with the human genome sequence will help researchers to narrow their search for many more of the genetic contributors underlying cancer and other major diseases.”
Genetic Compass
Efforts to create the genetic tools needed for mapping disease genes in dogs have gained momentum over the last 15 years, and already include a partial survey of the poodle genome. More than two years ago, Kerstin Lindblad-Toh, PhD, co-director of the genome sequencing and analysis program at the Broad Institute, and colleagues embarked on a two-part project to assemble a complete map of the dog genome.
First, they acquired high-quality DNA sequence covering nearly 99 percent of the dog genome from a female boxer named Tasha. The boxer was chosen as a representative of the average purebred dog to produce what has become a reference sequence for the dog-genome community.
Using the sequence information as a genetic “compass,” they navigated the genomes of 10 different dog breeds and other related canine species, including the gray wolf and the coyote.
The researchers identified roughly 2.5 million single nucleotide polymorphisms, or SNPs, sprinkled throughout the dog genome. SNPs are variations in the DNA code, some of which contribute to diseases or the overall health of a dog.
SNPs also can be used to create a set of coordinates with which to survey genetic changes, both within and across dog breeds. These efforts revealed that individual breeds have maintained a large amount of genetic variability, despite their long history of restrictive breeding.
In practical terms, this means that future efforts to locate disease genes in dogs can be much narrower in scope than comparable human studies, requiring a smaller number of genetic markers and DNA samples collected from the blood or cheek from only a few hundred dogs.
“Of the more than 5,500 mammals living today, dogs are arguably the most remarkable,” says senior author Eric Lander, PhD, director of the Broad Institute at of MIT and Harvard. He is a professor of biology at MIT and systems biology at Harvard Medical School, as well as a member of the Whitehead Institute for Biomedical Research.
“The incredible physical and behavioral diversity of dogs — from Chihuahuas to Great Danes — is encoded in their genomes. It can uniquely help us understand embryonic development, neurobiology, human disease and the basis of evolution,” Dr. Lander notes.
Powerful Tool
“When compared with the genomes of human and other important organisms, the dog genome provides a powerful tool for identifying genetic factors that contribute to human health and disease,” says Francis S. Collins, MD, PhD, director of the National Human Genome Research Institute (NHGRI), which supported the research.
“This milestone is especially gratifying because it will also directly benefit veterinary researchers’ efforts to better understand and treat diseases afflicting our loyal canine companions,” Dr. Collins adds.
Humans domesticated the dog, Canis familiaris, from gray wolves as long as 100,000 years ago. As a result of selective breeding over the past few centuries, modern dog breeds present a model of diversity. From six-pound Chihuahuas to 120-pound Great Danes, from high-energy Jack Russell Terriers to mild-mannered basset hounds, and from Shetland sheepdogs with their herding instincts to pointers inclined to point, humans have bred dogs for desirable physical and behavioral traits.
Such breeding practices preserve preferred traits of one generation in the next, but they also predispose many dog breeds to genetic disorders, including heart disease, cancer, blindness, cataracts, epilepsy, hip dysplasia and deafness.
The research group found that while different breeds show amazing physical diversity, they often share large segments of their DNA, likely reflecting their recent shared origin. As a result, genetic tools being developed at the Broad Institute and NHGRI for any one breed of dog are likely to be useful in genetic experiments in nearly any breed.
Evolutionary Tree
While dogs occupy a special place in human hearts, they also sit at a key branch point, relative to humans, in the evolutionary tree. It was already known that humans share more of their ancestral DNA with dogs than with mice. The availability of the dog genome sequence has allowed researchers to describe a common set of genetic elements — representing about 5 percent of the human genome — that are preferentially preserved among human, dog and mouse.
Rather than being evenly distributed, some of these elements are crowded around just a small fraction of the genes in the genome. Future studies of these clusters may give scientists the critical insight needed to unravel how genomes work.
Elaine A. Ostrander, PhD, chief of NHGRI’s Cancer Genetics Branch, is a co-author of the Nature paper, along with postdoctoral research fellows, Heidi G. Parker and Nate B. Sutter. In addition, Dr. Ostrander is the lead author of the white paper that sets forth the biomedical rationale for sequencing the dog genome.
Dr. Ostrander’s laboratory maps genes responsible for susceptibility to cancer — including breast and prostate cancers — in canines and humans.
“The leading causes of death in dogs are a variety of cancers, and many of them are very similar biologically to human cancers.” says Dr. Ostrander. “Using the dog genome sequence in combination with the human genome sequence will help researchers to narrow their search for many more of the genetic contributors underlying cancer and other major diseases.”
Genetic Compass
Efforts to create the genetic tools needed for mapping disease genes in dogs have gained momentum over the last 15 years, and already include a partial survey of the poodle genome. More than two years ago, Kerstin Lindblad-Toh, PhD, co-director of the genome sequencing and analysis program at the Broad Institute, and colleagues embarked on a two-part project to assemble a complete map of the dog genome.
First, they acquired high-quality DNA sequence covering nearly 99 percent of the dog genome from a female boxer named Tasha. The boxer was chosen as a representative of the average purebred dog to produce what has become a reference sequence for the dog-genome community.
Using the sequence information as a genetic “compass,” they navigated the genomes of 10 different dog breeds and other related canine species, including the gray wolf and the coyote.
The researchers identified roughly 2.5 million single nucleotide polymorphisms, or SNPs, sprinkled throughout the dog genome. SNPs are variations in the DNA code, some of which contribute to diseases or the overall health of a dog.
SNPs also can be used to create a set of coordinates with which to survey genetic changes, both within and across dog breeds. These efforts revealed that individual breeds have maintained a large amount of genetic variability, despite their long history of restrictive breeding.
In practical terms, this means that future efforts to locate disease genes in dogs can be much narrower in scope than comparable human studies, requiring a smaller number of genetic markers and DNA samples collected from the blood or cheek from only a few hundred dogs.
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