Journal : Severe Acute Respiratory Syndrome Coronavirus Infection Causes Neuronal Death in the Absence of Encephalitis in Mice Transgenic for Human AC

Jason Netland,¹ David K. Meyerholz,² Steven Moore,² Martin Cassell,³ and Stanley Perlman^1,4*

Journal of Virology, August 2008, p. 7251, Vol. 82, No. 15
0022-538X/08/$08.00+0 doi:10.1128/JVI.01175-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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Interdisciplinary Program in Immunology,¹ Departments of Pathology,² Anatomy and Cell Biology,³ Microbiology, University of Iowa, Iowa City, Iowa 52242⁴

Received 3 April 2008/ Accepted 12 May 2008

Infection of humans with the severe acute respiratory syndrome coronavirus (SARS-CoV) results in substantial morbidity and mortality, with death resulting primarily from respiratory failure. While the lungs are the major site of infection, the brain is also infected in some patients. Brain infection may result in long-term neurological sequelae, but little is known about the pathogenesis of SARS-CoV in this organ. We previously showed that the brain was a major target organ for infection in mice that are transgenic for the SARS-CoV receptor (human angiotensin-converting enzyme 2). Herein, we use these mice to show that virus enters the brain primarily via the olfactory bulb, and infection results in rapid, transneuronal spread to connected areas of the brain. This extensive neuronal infection is the main cause of death because intracranial inoculation with low doses of virus results in a uniformly lethal disease even though little infection is detected in the lungs. Death of the animal likely results from dysfunction and/or death of infected neurons, especially those located in cardiorespiratory centers in the medulla. Remarkably, the virus induces minimal cellular infiltration in the brain. Our results show that neurons are a highly susceptible target for SARS-CoV and that only the absence of the host cell receptor prevents severe murine brain disease.

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* Corresponding author. Mailing address: Department of Microbiology, University of Iowa, BSB 3-712, Iowa City, IA 52242. Phone: (319) 335-8549. Fax: (319) 335-9999. E-mail: stanley-perlman@uiowa.edu Published ahead of print on 21 May 2008.

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article : What the VIROLOGY ?

study of viruses and their role in disease. Many viruses, such as animal RNA viruses and viruses that infect bacteria, or bacteriophages, have become useful laboratory tools in genetic studies and in work on the cellular metabolic control of gene expression (see nucleic acids). Because viruses can sometimes carry extra genetic material into host cells, they have been used to experimentally transfer genetic material, specifying a particular enzyme, into nuclei of mammalian host cells that lacked the ability to synthesize that enzyme. The ability of viruses to transfer genetic material has also been extensively studied in bacteria (see recombination). Virus-mediated gene transfers are medically interesting because of the possibility that in the future enzyme-specifying genes might be transferred into humans with hereditary enzyme-deficiency diseases. Virus interference is a phenomenon in which host cells, while infected by one virus, are protected against infection by other viruses; the technique has been used experimentally as a form of temporary immunization. Interferon, a vast number of proteins produced by virus-infected cells that inhibits viral replication within the cell has been studied with a view toward preventing or controlling virus-caused diseases. Viruses continue to be investigated because they are held to be possible causative agents of some human cancers, and because under certain conditions the body's immune response to virus infection may cause tissue damage and develop into an autoimmune disease. Viruses can have high rates of mutations (point mutations) that keep them undetectable. Human immunodeficiency virus (HIV), the virus associated with AIDS, is a retrovirus that appears to have mutated into a number of strains that attack the immune system and produce viral-induced immunosuppression.

____________________The Columbia Encyclopedia, Sixth Edition Copyright© 2004, Columbia University Press. Licensed from Lernout & Hauspie Speech Products N.V. All rights reserved

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article : The Group Animal of Reptiles

By Regina Bailey, About.com
Reptiles have been around for a long time. They are believed to have evolved from amphibians and have developed several adaptations for life out of water. Reptiles range in size from the green anole (5 to 8 inches) to the crocodile (23 feet). Reptiles can also live in habitats ranging from swamps to deserts. This great diversity among reptiles is one of the reasons they have managed to survive.

One major characteristic of reptiles is the presence of scales composed of a protein called keratin. These scales form a waterproof barrier of skin, which allows reptiles to exist away from water without the threat of dehydration. Another characteristic is the regulation of internal body temperature by the external absorption of heat. Thus, reptiles are ectothermic. Unlike endothermic creatures, which must use calories from food to regulate body temperature, reptiles don't require much food to maintain body temperature and survive.

Reproductively, they can lay eggs on land due to the development of a protective shell around the egg. However, these eggs must be fertilized inside the female before the shell forms.

The reptilia class can be divided into three main orders: squamata, chelonia, and crocodilia.

Squamata (includes lizards and snakes)

• Lizards outnumber all other reptiles. They are generally small and very diverse.
  
  
• Snakes are closely related to lizards. They can detect vibrations, and some can sense changes in temperature.
  
  

Chelonia

• Turtles have a hard protective shell. Most live on land or must return to land to lay their eggs.
  
  

Crocodilia (alligators and crocodiles)

• These creatures live mostly in the water and are generally the largest of the reptiles.
  
  

The crocodilians are thought to be the closest living relative of the dinosaurs among reptiles. Along with birds, dinosaurs and crocodilians are descendants of a group of ancient reptiles known as the thecodonts. Snakes, lizards, and turtles appear to have evolved separately from the thecodonts.

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article : You Know, Just Time Has Newborn Dolphins Are Active 24/7

By Laura Klappenbach, About.com

Scientists have discovered that baby dolphins and infant orcas are insomniacs. The newborn cetaceans remain active around the clock for the first month of their lives. As a result, their mothers are deprived of sleep as well. Gradually, over the course of several months, the newborns and their mothers both increase their sleep time until they reach a normal level of sleep.

There may be significant advantages to young cetaceans that remain active for the first few weeks after birth. Constant activity may reduce the dangers posed by predators—by not sleeping, the young simply do not let their guard down. It may also help to maintain high body temperature until the young animal can pack on a sufficient layer of blubber. Additionally, the young cetaceans must surface more frequently than adults to breathe and staying awake all night may ensure they are better able to surface as much as is needed. Finally, the extended period of wakefullness may enable the young cetaceans a period of rapid growth and development.

Dr. Jerome Siegel, professor-in-residence at the Semel Institute for Neuroscience and Human Behavior at UCLA and chief of neurobiology research at the VA Greater Los Angeles Healthcare System described the findings and their implications:

"Somehow these seafaring mammals have found a way to cope with sleep deprivation, facilitating rather than hindering a crucial phase of development for their offspring. Their bodies have found a way to cope, offering evidence that sleep isn't necessary for development and raising the question of whether humans and other mammals have untapped physiological potential for coping without sleep."

The research project was conducted by a group of neuroscientists from UCLA and the VA Greater Los Angeles Health Care System. The team observed two adult female killer whales and their calves and four dolphins and their calves; all of the animals that were studied were observed in captivity.

Find out more: Behavioral Aspects of Sleep in Bottlenose Dolphin Mothers and Their Calves (UCLA)

Photo © Debra McGuire / iStockphoto.

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article : Are you know, What the Sexusl Dimorphism?

By Laura Klappenbach, About.com

Question: What is Sexual Dimorphism?

Answer: Sexual dimorphism is the difference in form between male and female members of the same species. Sexual dimorphism includes differences in size, coloration, or body structure between the sexes. For example, the male northern cardinal (Cardinalis cardinalis) has a bright red plumage while the female has a duller plumage. Male lions (Panthera leo) have a mane, female lions do not. Below are some additional examples of sexual dimorphism:

• Male elk (Cervus canadensis) grow antlers, while female elk do not have antlers.
• Male elephant seals (Mirounga sp.) develop an elongated snout and fleshy nose that they inflate as a sign of aggression when competing with other males during the mating season.
• Male birds of paradise (Family Paradisaeidae) are noted for their elaborate plumage and complex mating dances. Females are far less ornate.

In most cases when size differences exist between the male and female of a species, it is the male that is the larger of the two sexes. But in a few species, such as birds of prey and owls, it is the female is the larger of the sexes and such a size difference is referred to as reverse sexual dimorphism. One rather extreme case of reverse sexual dimorphism exists in a species of deepwater anglerfish called the triplewart seadevils (Cryptopsaras couesii). The female triplewart seadevil grows much larger than the male and develops the characteristic illicium that serves as a lure to prey. The male, about one tenth the size of the female, attaches itself to the female as a parasite.

Sources

• Folkens, P. 2002. National Audubon Society Guide to Marine Mammals of the World. New York: Alfred A. Knopff.
• Sexual Dimorphism. 2007 (Accessed online). Wikipedia.

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article : Eukaryote, define and content

By Laura Klappenbach, About.com
Definition: n. Eukaryotes are organisms made up of cells that possess a membrane-bound nucleus (that holds genetic material) as well as membrane-bound organelles. Genetic material in eukaryotes is contained within a nucleus within the cell and DNA is organized into chromosomes. Eukaryotic organisms may be multicellular or single-celled organisms. All animals are eukaryotes. Other eukaryotes include plants, fungi, and protists.

Sources:

• Burnie, D. and D.E. Wilson. 'Animal'. Dorling Kindersley. London. 2001.
• Keeton, W.T. and J.L. Gould. 'Biological Science (4th Edition)'. W.W. Norton & Co Ltd. New York. 1986.

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article : More Study of Comparing Prokaryote and Eukaryote Cells from Differences in Cell Structure

By Laura Klappenbach, About.com

All living organisms can be sorted into one of two groups depending on the fundamental structure of their cells. These two groups are the prokaryotes and the eukaryotes.

Prokaryotes

Prokaryotes are organisms made up of cells that lack a cell nucleus or any membrane-encased organelles. This means the genetic material DNA in prokaryotes is not bound within a nucleus. Additionally, the DNA is less structured in prokaryotes than in eukaryotes. In prokaryotes, DNA is a single loop. In Eukaryotes, DNA is organized into chromosomes. Most prokaryotes are made up of just a single cell (unicellular) but there are a few that are made of collections of cells (multicellular). Scientists have divided the prokaryotes into two groups, the Bacteria and the Archaea.

Eukaryotes

Eukaryotes are organisms made up of cells that possess a membrane-bound nucleus (that holds genetic material) as well as membrane-bound organelles. Genetic material in eukaryotes is contained within a nucleus within the cell and DNA is organized into chromosomes. Eukaryotic organisms may be multicellular or single-celled organisms. All animals are eukaryotes. Other eukaryotes include plants, fungi, and protists.

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article : Population Biology in Growth and Regulation

By Laura Klappenbach, About.com

Populations are groups of individuals belonging to the same species that live in the same region at the same time. Populations, like individual organisms, have unique attributes such as:

• growth rate
• age structure
• sex ratio
• mortality rate

Populations change over time due to births, deaths, and the dispersal of individuals between separate populations. When resources are plentiful and environmental conditions appropriate, populations can increase rapidly. A population's ability to increase at its maximum rate under optimal conditions is called its biotic potential. Biotic potential is represented the letter r when used in mathematical equations.

In most instances, resources are not unlimited and environmental conditions are not optimal. Climate, food, habitat, water availability, and other factors keep population growth in check due to environmental resistance. The environment can only support a limited number of individuals in a population before some resource runs out or limits the survival of those individuals. The number of individuals that a particular habitat or environment can support is referred to as the carrying capacity. Carrying capacity is represented by the letter K when used in mathematical equations.

Populations can sometimes be categorized by their growth characteristics. Species whose populations increase until they reach the carrying capacity of their environment and then level off are referred to as K-selected species. Species whose populations increase rapidly, often exponetially, quickly filling available environments, are referred to as r-selected species.

Characteristics of K-selected species include:

• late maturation
• fewer, larger young
• longer life spans
• more parental care
• intense competition for resources

Characteristics of r-selected species include:

• early maturation
• numerous, smaller young
• shorter life spans
• less parental care
• little competition for resources

Some environmental and biological factors can influence a population differently depending on its density. If population density is high, such factors become increasingly limiting on the success of the population. For example, if individuals are cramped in a small area, disease may spread faster than it would if population density were low. Factors that are affected by population density are referred to as density-dependent factors.

There are also density-independent factors which affect populations regardless of their density. Examples of density-independent factors might include a change in temperature such as an extraordinarily cold or dry winter.

Another limiting factor on populations is intraspecific competition which occurs when individuals within a population compete with one another to obtain the same resources. Sometimes intraspecific competition is direct, for example when two individuals vie for the same food, or indirect, for example when one individual's action alters and possibly harms the environment of another individual.

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article : How We Know The Working zoologist ?

Five Career Twists for Animal and Wildlife Enthusiasts

By Laura Klappenbach, About.com

Do you ever wonder how to employ your love of animals and wildlife? Many zoologists and wildlife enthusiasts participate in research or teach at universities. While these careers are rewarding and enjoyable, they are not for everyone. If you would like to expand your job horizons beyond the university setting, here are five career options for you to consider.

1. Zookeeper

A zookeeper, employed by a zoo or aquarium, is responsible for caring for animals and their enclosures. A zookeeper's activities include preparing meals, cleaning enclosures, and monitoring animal behavior. Depending on the animal in question, a zookeeper might also groom and exercise animals.

2. Animal and Wildlife Educator

Zoos, aquariums, parks, and museums employ educators and program developers to create a variety of materials—brochures, videos, guided tours, exhibits—to educate visitors about animals and wildlife. Opportunities range from volunteer positions to full-time staff positions. As an educator, you can also create content for books, magazines, newspapers, and web-media.

3. Zoo Curator

Zoo curators are responsible for the acquisition of animals. Zoos acquire animals primarily through captive breeding programs. Occasionally, animals are traded among zoos or, on rare occasions, collected from the wild. The collection, trade, and transport of animals is regulated by government agencies; consequently the zoo curator acts as a liaison between these agencies and the zoo. Additionally, the zoo curator plays a role in the administration of zoo functions and captive breeding programs.

4. Wildlife Rehabilitator

Wildlife rehabilitation is the process of caring for ill, injured or orphaned wild animals and releasing them back in to their habitat once able to care for themselves. A wildlife rehabilitator often steps in when human activity has caused harm to wildlife: oil spills, lumbering activity, trapping, hunting. Rehabilitators must acquire permits from state and federal wildlife agencies before they can possess or handle wildlife.

5. Animal Behaviorist

Animal behaviorists train zoologists and other zoo employees how to interact with and successfully care for animals. Animal behaviorists are often trained in ethology--the study of animal behavior--and have experience working first-hand with animals.

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article : Defining Zoology and Study in Science

Understanding the Science and Study of Animals

By Laura Klappenbach, About.com

Zoology is the study of animals, a complex discipline that draws upon a diverse body of scientific observation and theory. It can be broken down into numerous sub-disciplines: ornithology (the study of birds), primatology (the study of primates), ichthyology (the study of fish), and entomology (the study of insects), to name a few. As a whole, zoology encompasses a fascinating and important body of knowledge that enables us to better understand animals, wildlife, our environment, and ourselves

To embark upon the task of defining zoology, we explore the following three questions: (1) How do we study animals? (2) How do we name and classify animals? and (3) How do we organize the knowledge we acquire about animals?

How do we study animals?

Zoology, like all areas of science, is shaped by the scientific method. The scientific method--a series of steps that scientists take in order to acquire, test, and characterize the natural world--is the process by which zoologists study animals.

How do we name and classify animals?

Taxonomy, the study of the classification and nomenclature of living things, enables us to assign names to animals and to group them into meaningful categories. Living things are classified into a hierarchy of groups, the highest level being the kingdom, followed by the phylum, class, order, family, genus, and species. There are five kingdoms of living things: plants, animals, fungi, monera, and protista. Zoology, the study of animals, focuses on those organisms in the animal kingdom.

How do we organize our knowledge of animals?

Zoological information can be organized into a hierarchy of topics that focus on different levels of organization: the molecular or cellular level, the individual organism level, the population level, the species level, the community level, the ecosystem level, and so forth. Each level aims to decribe animal life from a different perspective

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article : Understanding and Content the Study of Animals

An Introduction to Zoology

By Laura Klappenbach, About.com

Zoology is the study of animals (Gr. zoon, animal + logos, to study). This sounds like a simple definition, but upon further clarification, the "study of animals" turns out to be a broad and complex subject matter. The "study of animals" calls upon many other scientific disciplines including:

• biology
• chemistry, biochemistry, and molecular biology
• genetics
• population biology
• evolution and paleontology
• comparative anatomy
• ethology
• ecology, biogeography, and conservation biology

Like all forms of life on our planet, animals have changed over the course of millions of years. To help in the understanding of our planet's history, time is broken down into the following units (in order of descending duration):

• Eon
• Era
• Period
• Epoch

The three eons of Earth's history include the Archean Eon (4600 - 2500 Ma YBP*), the Proterozoic Eon (2500-590 Ma YBP), and the Phanerozoic Eon (590-0 Ma YBP). The Phanerozoic Eon differs from the preceeding Archean and Proterozoic Eons by a sharp increase in the diversity of multicellular lifeforms. During Phanerozoic Eon, notable events in animal evolution include:

• First vertebrates appeared (Paleozoic Era, Cambrian Period)
• Fishes and invertebrates diversified (Paleozoic Era, Ordovician Period)
• First terrestrial plants and animals (Paleozoic Era, Silurian Period)
• First amphibians (Paleozoic Era, Devonian Period)
• First reptiles (Paleozoic Era, Carboniferous Period)
• Insects and reptiles diversify (Paleozoic Era, Permian Period)
• Reptiles diversify, first dinosaurs (Mesozoic Era, Triassic Period)
• First mammals, first birds, dinosaurs dominate then mass extinction event (Mesozoic Era, Jurassic Period)
• Origin of human family (Cenozoic Era, Tertiary Period, Pliocene Epoch)

* Please note: The notation 'Ma YBP' indicates "million years before present".

A fundamental requirement for the study of animals, is a classification system; a way of assigning names and illustrating relatedness between animals. This naming system, called bionomial nomenclature assigns a two-part name to each organism (this naming convention is applied to all lifeforms, not just animals). The two-part name is based on the organism's genus and species (the two most granular levels of classification). The full classification of an organism includes its placement into the following heirarchy (groups listed below in order of ascending specificity):

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

The body of scientific fact and theory that comprises zoology, like all other sciences, has been acquired (and continues to expand) by the application of the scientific method. The scientific method is an approach to gathering, interpretting, and applying facts and observations to expand our knowledge of the world around us. The scientific method is a process consisting of the following basic steps:

1. Make observations
2. Formulate hypothesis (or question)
3. Design an experiment (that will answer the question)
4. Perform experiment and collect data
5. Interpret data
6. Form conclusions

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