Protist Pathogens in Humans

Plasmodium gallinaceum (Malaria) in mosquito gut; Credit: Wikimedia

Protists are a biologically diverse group of eukaryotic organisms. They are generally considered to be single celled and lack any of the specialized tissues associated with more complex groups of organisms, but these are their only defining features – without looking genetically. Their metabolism can be phototroph or organotroph, and the way they reproduce varies wildly depending on the specific species.

They might be difficult to define, but their role as pathogens is more certain. Some species will act as pathogens to plants, others to animals, but perhaps the most well-known are those in the Plasmodium genus, which can cause malaria in humans.

Toxoplasma Makes Mice Lose Fear of Cats

A mouse infected with the Toxoplasma parasite loses its fear of cats; Credit: Wendy Ingram

The Toxoplasma protozoan parasite is not only a hazard for pregnant women, few are aware of how it also affects the behavior of mice. Infected mice actually seem to lose their fear of cats, which is not only beneficial to felines, whom receive an easy meal, but allows the parasite to complete its life cycle within the cat's gut.

The mind altering effects appear to be permanent and persist long after the mouse has recovered from the initial onset of toxoplasmosis. This appears to be true even when the parasites cysts are not present in the brain, indicating that a permanent change has been made. Wendy Ingram at the University of California, Berkeley speculates that the section of the brain responsible for smell has been damaged, meaning mice can no longer sense cat urine.

The research is particularly interesting because it's believed that up to one-third of the world's population has been exposed to the Toxoplasma parasite. A healthy immune system will keep the dormant cysts under control for most, but immunocompromised individuals may have health concerns. There is even reason to believe that chronic infection is linked to schizophrenia and suicidal behavior.

Sources:
PLOS ONE
Eisenlab.org

An Overview of Sex-Linked Disorders

Sex-linked disorders are any diseases, disorders, or abnormal conditions that are caused by one or more defective genes on the X chromosome. The X chromosome is one of the two sex chromosomes, the other being the Y chromosome. In humans, males have XY chromosomes and females have XX chromosome. Sex-linked disorders may also include an aberration in the number of X or Y chromosomes.

The Immune System Cells: The Basic Units of Our Body's Defense

Macrophage

The human body is constantly under attack by infectious agents, also called ‘pathogens’. Luckily our body has an intricate multi-systemic defense mechanism, that we call ‘the immune system’. Immunologists divide this immune system into two; innate immunity and acquired or adaptive immunity. The immune system has many different types of cells. These cells come from two main progenitors, or ancestor cells; myeloid progenitor cell and lymphoid progenitor cell.

Infectious Organisms that Fight Over You

Hookwork Larva

Anthropologists Aaron Blackwell and Michael Gurven of UC Santa Barbara, studying the indigenous Tsimane people, located in Bolivia made a rather remarkable discovery about those infected by worms, known as helminths. They were less likely to also be host to giardia, a protozoan parasite. Whats also interesting is that the opposite is true, those infected by giardia, were less likely to have intestinal worms.

What's more, when someone was treated for either, they were more likely to have the other later on, further indicating that these two parasites vie for control of the host. While these findings are interesting they are also important for a few reasons. Primarily it means health care providers must reevaluate the methods for dealing with parasites.

This is especially important in developing countries where large numbers of the population have parasitic worms and costly programs are often implemented to treat them. Even with treatment, if sanitary conditions don't improve reinfection by the same organism is very likely. According to Gurven, "if intestinal worms are protective against giardia, there's a tradeoff, and then the question is, which of the two is worse?"

The study represents data collected over six years on more than 3,000 Tsimane individuals. More information on their work can be found at University of California - Santa Barbara.

Mice Successfully Used as Model Organisms for Sexual Transmission of HIV

Mouse; credit: Martha Sexton

While HIV is no longer the death sentence it once was thanks to antiretroviral drugs, it still remains a scourge in many parts of the world. The use of model organisms is important in understanding specific biological processes and although their use is not new within HIV/AIDS research, none have specifically replicated vaginal transmission of the disease. Researchers, Mary Jane Potash and colleagues from St. Luke's-Roosevelt Hospital Center and Columbia University Medical Center were able to successfully use a modified version of the virus to infect rodents that subsequently spread it via intercourse.

The virus is most commonly transmitted among humans via sex and this allows researchers to observe this process without artificially infecting individuals. This is actually very important because scientist believe, and previous research has implied, that certain factors during intercourse such as seminal fluid interacting with the female reproductive organs have an impact on infection rates.

Scientists are also able to more accurately study the effect of potential vaccines and retroviral drugs. For example they were able to confirm that female mice treated with retrovirals prior to mating were less likely to infect their partner. There is also evidence that hormones might have an effect on transmission since mice in estrus were less likely to transmit the virus. Scientists are drawing comparisons with human females during their menstrual cycle.

You can find a bit more info here: eurekalert.org

Intestinal Protein That "Lets the Good Bacteria In"

The bacterial pathogen C. rodentium (green) is covering the intestinal surface (blue) in mice; Credit: Vallance Lab, UBC

A new study at the University of British Columbia reminds us that our body is really quite the complex system. We've probably all heard that one of the consequences of our society of antibiotic abuse is a general trend towards more drug-resistant bacteria. Well a more immediate threat of overdoing it with antibiotics is you'll be killing off all the beneficial bacteria found naturally in the human gut.

Mobile Phone Use Causes Cancer...Maybe

Every now and again a story pops up in which scientists question just how healthy those mobile phones we suddenly seem to be addicted to really are. So do cell phones really cause cancer? The answer is pretty much the same as it's always been. Anything in excess is probably not good for a number of reasons. Cell phones, besides being a contributing factor to car accidents are also possibly a mild carcinogen. Although studies are ongoing, the IARC (International Agency for Research on Cancer) does categorize the device as "possibly carcinogenic".

While that's smack in the middle of their threat scale, it's still entry level and somewhat vague since the previous are "not classifiable as to its carcinogenicity to humans" and "probably not carcinogenic to humans". The current research at Tel Aviv University involves measuring "oxidative stress" levels in saliva of individuals classified as heavy users. The original train of thought being that cell phones are placed close to the users salivary gland so the saliva would indicate if anything out of the ordinary was happening. In fact oxidative stress levels were higher in heavy users, which is important because that leads to cell damage, including DNA, which can result in cancer causing errors.

Despite the findings I think it's safe to say we all know a few people who could stand to cut back on the cell phone use. You can check out the full article at eurekalert.org

Groundbreaking Study Might Save Millions Infected by HIV

According to the head of the Therapeutic and Vaccine Research Program at the Kirby Institute of New South Wales, Professor Sean Emery, extensive testing has proven that individuals suffering from HIV can reduce treatment dosage of antiretrovirals by a third and still have the same results as a full dose. What this means is that current AIDS funding and resources can be stretched to encompass many more individuals. More info can be found at biologynews.net