Human Egg Candling?

A while back on my personal blog I lamented our lack of ability to look at the chromosomes of an egg before it was fertilized. I spun an elaborate fantasy about a noninvasive human egg candling procedure that would tell if a particular egg might have some kind of chromosomal aberration (like Down's Syndrome).

Well, my fantasy remains pretty outlandish, but it turns out that there is a way to look at the genetic make-up of the egg before it is fertilized. I just wanted to make sure it had the proper number and right kinds of chromosomes but it can also be used to look into more specific things. The main reason it is used is to make sure that the egg is viable before implantation. This can cut back on the number of embryos they have to implant after in vitro fertilization in the hopes of having a healthy baby and hopefully, reduce the number of women who go from not having any baby at all to having four all at once.

The way it is done is to take the polar body out of the egg and do genetic testing on it. You might remember that in the process of reducing the number of chromosomes to half that of a regular cell, the egg produces these little things called polar bodies. Normally they disintegrate after the egg is fertilized but they contain the mirror half of the chromosomes that are in the egg. If there are any chromosomal abnormalities, you'd be able to tell from the polar body.

Of course, not everybody can afford IVF in the first place, but for those that can this might be a way to ensure that a woman my age (36) has a healthy baby. Most of us will probably just have to muddle along with nature and hope for the best... at least for now.

Links:

An abstract from a study about a possible function of polar bodies.

All about meiosis: scroll all the way down to see oogenesis.

Word Of The Day

gemetogenesis: The making of gametes. Gametes are the sex cells, or eggs and sperm. Sometimes you hear this referred to as spermatogenesis or oogenesis, meaning egg or sperm production. They are not produced in exactly the same way, which makes sense if you think about it. Eggs are large and have lots of cytoplasm. For the first divisions after fertilization there is no time for growth, so you end up with lots of cells the same size as the original egg. Sperm are little and have flagella so they can swim and find the egg. They don't contribute much (just the chromosomes they carry) to the size of the fertilized egg.

Slime and Cytoplasm

(Image from this award winning young scientist's web page.)

The first time I saw real live amoeba in my undergraduate biology lab class I was so excited that I went home and told my family... who reacted with blank stares and shrugs, but really... cells that move around by what looks like a magical oozing motion are cool.

How do they do that? It seems that they have the same kinds of (or similar) proteins that our muscle cells have. These protein filaments can contract and make the cytoplasm move. It looks a lot more complicated than that to me, but that has always been the draw of these "wee beasties"... they act in what seem to be very complex ways.

You can see the same kind of thing happen without a microscope if you look at a plasmodial slime mold. Plasmodial slime molds are also protists, like the amoeba, but they fuse together and make what is essentially a really big cell that has a lot of nuclei in it. You can watch these things flow around without a microscope... and I still find it so exciting to watch that I wanted to share it with you.

In this You Tube Video you can see a slime mold start out in one lump and spread out to cover nearby objects... flowing in a complex-looking, fascinating, and slightly disgusting way.

Links:

Actin and Myosin in Nonmuscle Cells (from an online cell biology text)

You and 30 of your closest friends could culture your own slime mold for less than $1.00 each.

An Abstract from a paper about the toxicity of ethanol and some other chemicals on Plasmodial Slime Molds.

Word of The Day

Cytoplasm: The jelly-like contents of a cell.

Measurement

Since science is really only concerned with what is measurable, measurements of various kinds are very important and pop up all over the place in almost any study of anything, but the numbers are only as good as the equipment and the people using the equipment. If you need centimeters and all you have are rulers with inches on them, you're in trouble. Or you could have the fanciest gas chromatograph on the market but only somebody like me to use it. It wouldn't do you any good.

If you've ever needed a really straight line, you have experience with this. The saying goes "Measure twice. Cut once." If you want a straight line you probably need more than two measurements. You start at the edge of your material and go... say ten inches (Why are you using inches instead of centimeters, anyway?). You make four or so marks along the length at ten inches and then try to connect them, but they aren't really all lined up. Some are a little farther out than others and you end up making a "best fit" line, which, if you are really lucky, looks straight.

What you are lacking is precision. Your lines are all pretty close to ten inches so your accuracy isn't bad, but sometimes you marked toward at the far end of the little black measuring tick and sometimes at the close end, also the ruler might have been at a slight angle sometimes, making slight variations in the measurements. Precision is the ability to come up with the same answer over and over again when measuring the same thing over and over, and it has a lot to do with both the equipment and the training of the person using it.

Accuracy is important too. Just because you came up with ten inches on the dot, every time, doesn't mean you have ten inches. Your ruler could be wrong or you could be looking at it and seeing the number ten where it should be twelve because the six-year-old took a pen to your ruler.

Precision sounds wonderful. It's a word that makes me think of professionalism, but precision without accuracy can be disastrous. Just think of the surgeon that could make a cut within a millimeter of where he intended, but took out the wrong organ. A little more accuracy and a little less precision might make the patient a little more alive.

Links:

If you ever need to collect measurements for the EPA... here are the methods.

The National Institute of Standards and Technology's Center for Nanoscale Science and Technology.

Here's how Australia measures things.

Word of The Day:

Bias: There are several ways this word is used in statistics (and we are talking about some very simple statistics here) but in measuring things, your group of measurements would be biased if they were wrong in some way that caused them not to fall into a "normal" bell curve... for instance, if they were precise but inaccurate because of that pen mark on the ruler's number two that made the 12 look like 10.

Making Hydrogen

(the BMW hydrogen 7)

A group of scientists have figured out a seemingly easy way of getting hydrogen from water. They are using special clusters of aluminum atoms that are arranged in a way that allows them to act as catalysts.

Catalysts are very common in biology, so I know something about them. You do too, even if you don't realize it. Think about what happens when you pour hydrogen peroxide on a cut. It bubbles. Right? Why does it bubble?

Hydrogen peroxide has two hydrogen and two oxygen atoms in it (H2O2) and you have a catalyst called catalase in your body that helps free some of the oxygen, turning the peroxide into water and oxygen. A catalyst greatly decreases the energy and time required for a reaction to take place. In this case it's very dramatic. That hydrogen peroxide might turn into water and oxygen on its own... if left alone for a few decades... but add a little catalase and it happens in seconds. In your body catalysts are mostly proteins that "hold" onto the chemicals and apply pressure in just the way that encourages the chemicals to react in a specific way.

In the case of the aluminum (which is not a protein, but you knew that) it needs to be arranged in a cluster of atoms so that one of them has a tendency to accept electrons and another to donate electrons. This lets the water bind to the cluster and frees some hydrogen. Without the aluminum the reaction requires the addition of energy (heat or electricity) but with the aluminum clusters, the reaction can happen at room temperature. Now, if they can just figure out how to unbind the remaining oxygen and the extra hydrogen atom from the aluminum, they will be able to reuse the aluminum clusters over and over again.

Links:

Read all about it here.

Some facts about hydrogen as a fuel, from Stanford.

Phrase of The Day

Lewis Acid: A compound that can accept a pair of electrons. A Lewis Base can donate a pair of electrons. This is a slightly different than the definition of an acid as a chemical that has a pH less than 7.

Winter Fish Kill

(There were plenty of fish in this lake... they just didn't want to be caught.)

The only time I generally fish is on the summer backpacking trip I take with my husband every year. We go to remote places so that we won't have much company, but it's incredibly frustrating to spend two days backpacking up to some remote mountain lake only to find that there aren't any fish. We've had this happen even when oldtimers have assured us that there is indeed a fish population in a particular lake.

The first time this happened on one of our trips my husband just shrugged his shoulders and said, "I guess it was winter killed". I pictured it being so cold up there that the lake froze solid, killing the fish... not too hard to believe when you are up at dawn in July, in the mountains, wearing three layers, a stocking cap and gloves, and still a little too cold for comfort. Even so, it isn't likely that a fairly deep lake would freeze solid. So what kills fish during the winter?

When it gets cold the water on top of the lake freezes. This is handy, Ice floating like that, or it might really be likely to freeze solid. However, the ice on top of the lake restricts the ability of the lake to absorb oxygen. This isn't so bad because the fish's metabolism slows and they don't use as much oxygen as in the summer. As long as light can filter through the ice there will be some oxygen produced by the plants, but if it snows a lot then the snow will block the light. Eventually, if it doesn't melt off soon enough, the dissolved oxygen levels become so low that fish will start to die.

Unfortunately, it seems that trout (our fish of choice) are particularly sensitive to this. The population will eventually bounce back as long as there is a stream or something to connect the lake with other fish populations.

... and we can always spend the time taking lots of pretty pictures.

Links:

EPA's information about mercury in fish.

National Fish and Wildlife Foundation

The Nature Conservancy's program to map freshwater biodiversity.

Word Of The Day:

Biodiversity: The number of different kinds of living things in a given area.

ESO's VLT

(The center of a galaxy as seen by the VLT.)

Spend just a little time wandering around in the world of science and you'll run into a lot of esoteric acronyms that stand for very long and incomprehensible words. That's one reason I was intrigued by the VLT.

ESO is the European Southern Observatory, and VLT stands for Very Large telescope. There's an acronym I can live with.

The VLT is really four separate telescopes with mirrors 8.2 meters (26 feet and almost 11 inches) across. Each of these can be used alone, and generally they are used that way a lot, but when used together in groups (along with four smaller, movable Auxiliary Telescopes) they can greatly increase the resolution of an image. When they are used this way they are called an Interferometer.

Links:

A Really Excellent You Tube Video

An Explanation of Interferometry

Word of The Day

Resolution: The ability to distinguish two separate points as to distinct points rather than one big blur. The ESO website says that the VLT could see a car's headlights as two points if the car were on the moon.

Dementia

Dementia isn't really a disease, it's a set of symptoms that can be caused by lots of different things. Can't remember where you put your keys? Well, if everything else seems to be working okay then you probably don't have dementia. Dementia is when you have two or more problems with the way your brain works and the list of symptoms is quite extensive. A person with dementia might have hallucinations, language problems, motor skill problems, or emotional and personality problems to name just a few.

Alzheimer's disease is the disease that comes into my mind when I hear the word dementia but vascular problems and stroke can cause it also, and there are several other diseases and disorders that can cause it. The scary thing about dementia is that it can't usually be cured and it gets worse over time.

What I want to know is, what can I do to prevent it from happening to me. There are some computer games and mind bending puzzles and things on the market for that and I was wondering if they were helpful or not. Here is what I've learned about Dementia prevention.

1. Since stroke and vascular problems cause some kinds of dementia, the kinds of things that prevent those problems are helpful. Quitting smoking, exercising, stress reduction, and eating healthier are good ideas.

2. For the above reasons, it makes sense that statin drugs would be a good idea for those at risk. This study seems to support that idea.

3. Ginkgo doesn't seem to help, according to this study.

4 While no one particular mind game seems to have been studied, it does seem that using your brain regularly reduces your risk for dementia.

Links:

Leisure activities and the risk of Dementia in the elderly.

The National Institute of Neurological Disorders and Stroke

A List of Symptoms

Word of The Day

Aphasia: A loss of language ability. This is usually caused by damage to the brain and can occur in some kinds of dementia. It may only be the loss of some words or it could be an inability to use them properly.