About Amnesic Shellfish Poisoning

Amnesic shellfish poisoning, also known as ASP, is a rare disease caused by demoic acid that is usually found in razor clams, mussels and dungeness crab but it can be found in other shellfish as well. It is caused by a reddish brown plant that is found in saltwater. On the plant is a diatom called Nitzchia pungens. The toxins from this plant contaminate the shellfish in high doses, and when consumed by humans it can cause serious problems.

ASP was first discovered in 1987. Four people died in Canada after eating shellfish and many others got sick, some of which developed forms of amnesia. In the early 1990’s pelicans on California’s coast near Monterey became crazed and when tested were found to have large amounts of demoic acid in their system. ASP is one of four shellfish syndromes. The other three are Paralytic, Neurologic and Diarrheal.

What Are Diatoms and Domoic Acid?

Diatoms are unicellular organisms that are often found attached to filamentous algae. There are two major groups of diatoms, pennates and centric. Pennates are pen shaped diatoms and centric diatoms are cylinder shaped. Pennates are most likely to be found in freshwater, while the centric can usually be found in marine water. They are basically the brown slimy stuff found on rocks, wood, seaweed etc… that shellfish feed off of.

Domoic acid is a neurotoxin that naturally occurs in marine life and is found in diatoms. The condition caused by this disease is also sometimes called domoic acid poisoning or DAP. DAP can affect all mammals. Domoic acid has been found on the East coast, West coast and in the Gulf of Mexico.

Cause, Symptoms and Treatment of ASP

Shellfish eat the diatoms and during the filtering process retain some of the demoic acid. When there are large levels of algae in the water, shellfish secret less of the toxins, therefore making them more toxic. When humans consume the infected shellfish they get sick. This is a very rare disease, but it can cause:

  • Diarrhea
  • Severe abdominal pain
  • Vomiting
  • Nausea
  • Heart palpitations
  • Severe headaches
  • Permanent short-term memory loss
  • Coma
  • Death

Symptoms usually occur within 24 hours of consumption of infected shellfish. There is no antidote for demoic acid. Patients that develop symptoms after eating shellfish should seek medical attention immediately even though there is very little that can be done.

There is no way to tell if the shellfish is infected with demoic acid. There is no taste or odor associated with the contaminated seafood. State departments of health issue warning when unsafe levels of marine toxins have been found. ASP is usually present in late summer and early fall making that the best time to avoid shellfish consumption if there has been a large algae bloom on the coast.


The Eustachian Tubes: Maintaining Pressure in the Ear

Eustachian tubes, which are also sometimes known as the auditory or pharyngotympanic tubes, are small cartilage and bone canals. The canals connect the middle ear, which is an air-filled cavity in the internal structure of the ear, and the nasopharynx, the lower nasal cavity behind the mouth. This connection allows air movement into and out of the ear, maintaining the pressure inside the ear canal at the external atmospheric pressure.

Ear Pressure and Hearing

The function of the ear is to hear by converting sound waves to electrical impulses. Sound waves travel through the air and into the ear canal, where they proceed through the middle ear to vibrate the eardrum on the far end. The sound waves are then transmitted to the bones and structures of the inner ear, which are then responsible for transmitting the signals to the brain. Maintaining atmospheric pressure within the middle ear allows the sound waves to proceed unchanged.

Eustachian Tubes and Altitude

When the atmospheric pressure changes, there is sometimes a sensation in the ear as the pressure within the Eustachian tubes adjusts. When driving up a mountain or flying in an airplane, a popping sensation is often felt, hearing is impaired for a short period of time, or a popping sound is heard as the pressure adjusts. Swallowing, chewing, or yawning pulls on the neck muscles and can help the Eustachian tubes open, releasing the pressure in the ears.

Ear Drainage and the Nasal Cavity

The Eustachian tubes also allow mucus produced by the lining of the middle ear to drain. The mucus drains from the ear to the nasopharynx and then to the stomach, similar to the sinuses. The mucus is present to protect the ear from foreign material, similar to mucus in the nose and throat. Drainage prevents the ear from becoming clogged with this helpful material, which can affect hearing and increase the risk of ear infections.

In the case of respiratory illness, material can make its way from the nasal cavity to the ear through the auditory tubes. Blockage of the tube or tubes from a throat infection can result in an ear ache and potential spread of the infection to the inner ear.

Eustachian Tube Problems in Children

Children often have a more horizontally placed tube and may experience blocked drainage due to the anatomic position, resulting in a greater occurrence of ear infections. Doctors sometimes insert synthetic tubes to help keep the auditory tubes open and facilitate appropriate air and fluid exchange.

What Eustachian Tubes Do Not Do

The Eustachian tubes do not maintain balance per se; this is accomplished by hair cells in the inner ear. The pressure in the ear, though, can affect the function of the ear structures, so the auditory tubes play a role in maintaining the integrity of the system that maintains balance. Ear infections are known to affect equilibrium because of their clogging effect in the ear.

Similarly, swimmer’s ear is mistakenly attributed to problems with the Eustachian tubes. Water can become trapped in the ear canal and lead to an ear ache and dulled hearing, followed by inflammation and infection. The blockage prevents proper air movement to the ear drum, but is not a clogging of the auditory tubes.

A List of Marine Reptiles: Ocean Animals Include Crocodiles, Iguanas, and Snakes

Learn about marine iguanas in the Galapagos, tropical venomous seas snakes, the deadly salt water crocodile, and endangered sea turtles.

Asked to imagine a reptile and most people will think of lizards sunning in the desert, snakes slithering through the jungle, or geckos skittering in the corners of a human home. However, many reptiles spend their days gliding through tropical waters and migrating throughout the world’s oceans. A list of marine reptiles includes crocodiles, iguanas, snakes, and turtles.

Sea Turtles Come in Many Sizes

Sea turtles are one of the oldest species still alive today with fossils dating back 150 million years – meaning sea turtles roamed the Earth along with dinosaurs. Today there are seven recognized species of sea turtle and the Caribbean Conservation Corporation describes each species in detail. These marine reptiles come in a variety of sizes with the olive ridley weighing less than 100 pounds and the leatherback reaching 1,300 pounds. Sea turtles can travel thousands of miles in a lifetime migrating from their feeding grounds to their nesting beaches. Unfortunately, all seven species of this marine reptile are now endangered due to human poaching, destruction of habitat, and pollution.

Marine Iguanas of the Galapagos

The marine iguana (Amblyrhyncus cristatus) is endemic to the Galapagos Islands off the coast of Ecuador. As the National Geographic describes in its “Marine Iguana Profile” scientists believe that land dwelling iguanas from South America floated on logs millions of years ago to the Galapagos. These scary looking herbivores can grow up to five feet long and use their sharp teeth to scrape algae off of rocks. Cornell University describes in “Marine Iguanas” how these creatures can dive for an hour at a time although they usually remain submerged for 5 to 10 minutes. Unfortunately, human-introduced predators such as rats and dogs are threatening these fascinating creatures. The marine iguana is considered vulnerable to extinction.

Sea Snakes are a Highly Poisonous Marine Reptile

Sea snakes can be found throughout the tropical waters of the world from Africa to Southeast Asia to Panama. According to an August 2015 Science Daily article “Venomous Sea Snakes Play Heads or Tails with Predators” there are over 65 species in the ocean and all are highly poisonous. Sea snakes have one of the most toxic venoms known in all snake species. Active predators, the sea snake diet consists mostly of small fish found on coral reefs. Many species spend their entire lives at sea, although they tend to be found in shallow waters.

The Dangerous Saltwater Crocodile

Some say the saltwater crocodile is the animal most likely to eat a human, according to the National Geographic’s “Saltwater Crocodile Profile”. Living around Southeast Asia and the northern coastlines of Australia this marine reptile can reach 23 feet long and 2,200 pounds. It is the largest crocodilian in the world. Although they can swim far out to sea to feast on sharks, their prey mostly includes land-dwelling monkeys, boars, and wild buffalo. They are considered at a low risk for extinction however hunting and habitat loss has put pressure on their populations.

Protecting Marine Reptiles

Humans have put pressure on the populations of many marine reptile species. Hunting, habitat destruction, and pollution are pushing sea turtles and marine iguanas ever closer to extinction. Although the saltwater crocodile is considered safe at the moment the tide may turn if hunting and habitat loss continue. Although reptiles may not be as charismatic as pandas or tigers, they too deserve respect and have a right to exist in their homes.

Will Polio Be Eradicated?

Polio? What is polio? The only time the majority of people in our world encounter that name is when a physician encourages us to have our children immunized against polio. Polio or poliomyelitis is disease caused by a virus called the polio virus. The virus initially infects either the mouth or the intestines then gets into the bloodstream where it is carried to the spinal cord. Once in the spinal cord the virus reproduces causing damage to the nerves. In severe cases of poliomyelitis the patient becomes paralyzed. The polio virus is highly infectious and can be transmitted person-to-person by a fecal-oral route. There are three different types (P1, P2, and P3) of the polio virus that cause poliomyelitis and a person could theoretically have polio three different times since infection with one type of the virus does not protect against infection with the other types of the virus.

A fecal-oral route of transmission is a transmission route in which infected feces (excrement, bowel movement) from one person ends up in the mouth of an uninfected person. Many people do not wash their hands after using the restroom. After changing a diaper some people forget or are distracted and do not wash their hands.

Even though polio is rare today it was at one time a very common disease. Over 13,000 people each year developed the paralyzing form of polio in the United States during the 1940’s. Most of those with paralytic polio were children. Fortunately, even in that time, less than one in 100 people infected with polio developed paralysis. Most (95%) of the people infected with polio did not have any symptoms. Around 4-8% of people infected with polio had flu-like symptoms. Another 1-2% developed an infection of the membranes surrounding the brain (aseptic meningitis). All of those with flu-like symptoms got over the infection with no long-term problems and nearly every one that got aseptic meningitis were fine in 2 to 10 days. The major problems were associated with those that developed paralytic polio. Many people with paralytic polio got better and their muscles started functioning again. However, there were those every year that did not get better and were either paralyzed for life usually on one side or in some cases died. In the temperate regions of the world, summer was a common time to get polio and many parents kept their children at home in hopes of keeping them safe from polio.

It wasn’t until the mid 1950’s that the vaccine developed by Jonas Salk started to drastically reduce the number of polio victims in the world. Another vaccine developed by Albert Sabin (introduced in 1961) continued the decline in

What is a Pelvic Ultrasound? This Diagnostic Test Shows a Broad View of the Pelvis

Much like a transvaginal ultrasound, a pelvic ultrasound is a diagnostic test that gives views of a patient’s uterus, fallopian tubes, ovaries, and the surrounding areas. The difference between the two tests is that a pelvic ultrasound gives a broader, more general view. Often, a pelvic test will be performed first, followed by a transvaginal test. Other times a pelvic ultrasound is all that is necessary.

The preparation for a pelvic ultrasound involves filling the bladder about an hour before test time. Clear liquids (water, tea without milk, clear juices) work best because they produce less gas, an enemy to the ultrasound image.

Reasons for a pelvic ultrasound include:

Pain/ Irregular Bleeding

One of the most common reasons for a pelvic ultrasound is pelvic pain. Many women experience pain from fibroid tumors, ovarian cysts, endometriosis, pelvic infections, and a host of other reasons.

The transducer can capture the image of fibroids, benign uterine tumors. These tumors cause pelvic muscular cramping, especially during menstruation. They can also cause excessive bleeding.

An ovarian cyst, usually uncomplicated (benign), is a result of an egg ripening and not releasing. It can grow to as large as 6 cm or more, causing pain and pelvic pressure. A pelvic ultrasound is often the first test to be done, and if the ovary is not seen clearly, a transvaginal ultrasound might be done to determinine whether it is truly a cyst or a solid mass.

Endometriosis, or the overgrowth of endometrial tissue, can be found in unusual pelvic places, including the regions beyond the ovaries (adnexal), adjacent to the uterus, and even outside of the pelvis. It is thought that the endometrial tissue somehow migrates outside of the uterus through the fallopian tubes instead of being expelled into the vagina during menstruation. A pelvic ultrasound works best for diagnosing endometriosis because it gives a broad view of the areas around the pelvic organs.

Bladder Problems

Although a doctor might specifically order renal (kidney) and bladder ultrasounds for suspected bladder problems, occasionally an anomaly will be seen on a pelvic ultrasound. Because a patient has filled her bladder for this test, it is well-defined and viewable on a pelvic ultrasound. Bladder wall thickening (infections), ureter obstruction(s), and/or possible kidney stones can be detected, clarifying the reason for vague pelvic symptoms.

2nd and 3rd Trimester Pregnancies

Usually termed “obstetrical” ultrasounds, 2nd and 3rd trimester exams are performed in the same way as pelvic ultrasounds. A mother might fill her bladder somewhat less for a second trimester exam, and not at all for a 3rd trimester ultrasound, depending on her comfort level and the technologist’s needs.

This type of pelvic ultrasound shows fetal parts, determines fetal age, can determine fetal sex, and checks for the overall health of the fetus.

For further reference: WebMD

Why Our Food Rots II

This is the second edition of “Why our Food Rots.” To get you up to speed, last week’s article described what causes food to rot: MICROBES! I also mentioned the basic methods of food preservation and that changing the temperature of a food can either slow the growth of microbes or kill them. This week’s article will describe how various chemical treatments help in preserving food. The means of preserving food and the chemicals used to preserve the food are as follows:

  • pickling (salt or sugar; vinegar, a weak acid)
  • salting/sugaring
  • fermentation (alcohol)
  • chemical preservation (lots of compounds too long and hard to pronounce for now)

When people think of chemicals they usually think of compounds with long names that are poisonous to life. That is not really true. We are made up of chemicals. Salt and sugar are chemicals that are commonly found in our bodies. There are other chemicals that are not commonly found in us that can be deadly. Lead is a chemical that you don’t want in your body because it is very poisonous.

Unlike lead, chemicals like salt, and sugar are only poisonous in very very very high concentrations. Salt and sugar are also poisonous to microbes when in high concentrations. High concentrations of salt and sugar actually suck the water out of our cells and out of microorganism’s cells. When water levels get too low in a cell the cell will die because the enzymes in the cell can’t do their work. No enzymes working means no energy being produced. No energy leads to cell death.

There are a lot of examples of people using high concentrations of salt or sugar to preserve food. Beef jerky is one example. The meat is dried and salted to preserve it. Pickles are preserved in a salt brine that prevents the growth of microbes in and on the cucumbers. Vinegar is also used in salt brine to increase the acidity of the brine. Microbes are killed by acidic conditions because acid will also destroy the enzymes that make microbes grow. Jams, jellies and sweet pickles are examples of the use of sugar to preserve food.

These preservation techniques don’t kill us because we can lower the concentration of the salt or sugar by diluting them out with other foods we eat and because of the large mass of our bodies compared to the amount of salt or sugar we eat. Unfortunately for the microbes, their cell body mass is very small and as a result concentrations of salt and sugar that have little effect on us are deadly to them.

Functions and Structure of Ribosomes: Small Organelles that Carry Out the Process of Translation

Ribosomes are small organelles made of RNA and protein that carry out the important work of translating mRNA templates into proteins.

Ribosome Structure – Subunits of RNA and Protein

Ribosomes in eukaryotes are made up of two subunits, a large subunit, called 60-S, and a small subunit, named 40-S. In prokaryotes, the subunits are 50-S and 30-S.

These two subunits are made in the nucleus and join together in the cytoplasm to create the ribosome whenever mRNA is present and proteins need to be made. The two subunits join together, hook onto the mRNA and start protein synthesis. During the production of proteins, the larger subunit binds to tRNA and amino acids and the small subunit binds to the mRNA template. When the ribosome finishes reading the mRNA and making the protein, the two subunits break apart again.

Function of Ribosomes – Protein Construction

The function of ribosomes is to make proteins in a process called protein synthesis. The ribosomes combine amino acids, the building blocks of proteins, in the order specified by a messenger RNA (mRNA) template.

As the ribosome moves along the mRNA and reads the sequence, amino acids are attached to and organized by transfer RNA (tRNA), a special type of RNA that can bind to both the ribosome and amino acids.

Location of Ribosomes in the Cell – Free and Attached Ribosomes

Ribosomes come in two types, free ribosomes and membrane bound ribosomes, which can be found in different places within the cell and carry out slightly different versions of protein synthesis.

Free ribosomes are found floating in the cytosol of the cell, the liquid that fills the cell interior. Free ribosomes can move around in the cytosol and they generally make proteins for use inside the cell.

Membrane bound ribosomes, also called attached ribosomes, attach to the endoplasmic reticulum, creating rough endoplasmic reticulum, RER. These rough ER ribosomes make proteins that will be exported for use outside the cell or used in cell membranes. The proteins generated by ribosomes in the rough ER travel into the ER and are then packaged for transport to the plasma membrane to be incorporated there or sent outside the cell.

Ribosomes are capable of chaning between one type and another. Free ribosomes can become membrane-bound ribosomes and vice-versa depending on what the cell needs at any given time.

It is important for students of biology to understand the function and structure of ribosomes, since these important organelles carry out the steps of protein synthesis that create all of the proteins in the body. Without ribosomes, there would be no protein construction and no work could ever get done inside or out of the cell.