All Posts Filed in ‘Science

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Amygdalae and blogging

The telling of stories helps us to rewire the brain and reattach emotional significance to the memories we have. The act of being creative helps to balance the tendency to over-rely on logic as a coping mechanism. The act of doing this publicly is cathartic and enormously helpful

Mike Summerfield: The link between amygdalae and blogging

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Near miss

corrosive

I have worked in labs for a long time and it is generally a pretty safe work environment despite what some folks imagine. However, occasionally something happens that has the potential to turn pear-shaped.

Today I was making some 5 molar sodium hydroxide solution, which is corrosive. In fact, 1 molar sodium hydroxide is corrosive, 5 molar is five times stronger and so is very corrosive. It was also hot because the solution heats up as the solid dissolves. Without giving it too much thought, I covered the top of the measuring cylinder I was using and inverted it to mix. Unfortunately the combination of heat and alkaline solution dissolved part of the seal on the lid, resulting in a spurt of liquid bursting out and across my bench. Fortunately it went away from my face and didn’t hit anybody else so was mostly just a mess and some on my hand which was easily washed off.

In hindsight there were a few things I did wrong there: Inverting a measuring cylinder is a quick and dirty way to mix solutions but always has the potential for spills – I was taught better than that but have become slack over the years. It also was luck rather than good planning that caused the splash to go away from my face. I was wearing eye protection but probably should also have had a face shield on. Sodium hydroxide in the eyes is one of the worst accidents that can occur in a lab and the only reliable way to avoid it is to have protection between you and the corrosive liquid.

As with most mishaps I’ve had in labs over the years I was not injured, just got a fright. Whether that means I’m a safe worker or just stupid but lucky I’m not sure! It is good though to be reminded of the need to be careful and aware that something could potentially go wrong at any time.

photo of right hand with deep chemical burns from sodium hydroxide on the palm at base of thumb

What could have happened (Sodium hydroxide dermal burn)


Image of burn from: BMJ Case Rep. 2012; 2012: bcr2012007103. Published online 2012 September 11. doi:  10.1136/bcr-2012-007103

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Why do dogs eat grass?

I have an interesting article titled Why do dogs and cats eat grass? by Benjamin L. Hart which was published in the journal Veterinary Medicine (December 2008, 103, 12 pp648-649).

The author did several small surveys of students and customers who were dog owners based on the assumption that plant eating is associated with illness or dietary deficiency. The results indicated that illness was unlikely to be the reason for eating grass and that vomiting afterwards is not as common as thought.

To dig a bit deeper they used an online survey to ask dog owners about plant eating behaviour. With 1571 useful responses:

  • 67% said their dogs eat plants daily or weekly.
  • 8% reported their dogs showing signs of illness before eating plants.
  • 22% said their dog regularly vomits eating plants
  • Younger dogs are seen eating plants more often than older dogs

There was no indication that dogs with lower fibre in their diet ate plants more than other dogs.

Contrary to popular opinion, most dogs that eat grass or other plants are not unwell and most do not vomit afterwards. So why do they eat grass?

Worms

Both domestic and wild dogs eat plant material. It does not seem to be associated with illness or dietary deficiency but is a common behaviour so presumably serves some purpose.

The theory put forth by the author of this article is that eating plants helps purge parasites such as intestinal worms from the gut by increasing how quickly material moves through the gut and also by wrapping around the worms and carrying them out of the body

Sooo, about poo?

My question then is; why does my disgusting dog eat her own poo? She does eat grass but the theory of removing parasites is defeated by her coprophagy!

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Poison or Coke?

I’m looking at a paper written by some of my colleagues at the NZ National Poison Centre a few years back. This is an important topic for everyone to be aware of: Poisoning following exposure to chemicals stored in mislabelled or unlabelled containers: a recipe for potential disaster, by Yvette C Millard, Robin J Slaughter, Lucy M Shieffelbien, Leo J Schep; New Zealand Medical Journal 26th September 2014, Volume 127 Number 1403.

The problem

Every year people are accidentally poisoned due to hazardous substances being stored in the wrong containers or not being labelled properly. Often the substance is drunk from a bottle that is usually used for drink, such as soft drink, water, sports drink or milk bottles.

Who is at risk?

All age groups are at risk of poisoning in this way, but it is a particularly common way for adults to swallow nasty liquids by mistake. A common scenario is when the driver of a vehicle reaches for a drink bottle and inadvertently picks up a similar bottle containing oil, petrol or even antifreeze. Children are vulnerable because they associate the style of a food container with something they can eat or drink so are unaware of what it really contains.

How serious is this?

The consequences of this type of mistake can be fatal. There have been cases of people drinking paraquat by mistake because it had been kept in a drink bottle and this is almost inevitably fatal. Fortunately, most of the cases covered in by this study were unpleasant but not especially toxic.

Types of chemicals involved

Dishwashing liquid is very commonly stored in the wrong bottles. Petrol, diesel, two-stroke mix are also common culprits. Antifreeze, brake fluids, bleach, mineral turpentine, herbicides, methylated spirits, paint thinners, household cleaners all make the list. None of these are pleasant if you were expecting a refreshing drink of water or Gatorade.

It is illegal to store poisons in food containers

New Zealand food safety regulations explicitly prohibit storing chemicals or “any substance that could cause poisoning” in food containers, whether labelled or not. Yet still people do it. What I noticed in my time at the Poisons Centre is that this practise is surprisingly common in male-dominated workplaces (the list of chemicals involved backs this up). Maybe people think nobody is going to drink from a bottle on the shelf in the workshop anyway, or perhaps there is too much of a, “she’ll be right” attitude?

I do know that it shook all of us who were at work the day a call came through from a young man who had accidentally swallowed a mouthful of what turned out to be paraquat that was stored in a Coke bottle. We all knew his chances of surviving were not good.

ALWAYS KEEP POISONS IN THEIR ORIGINAL CONTAINERS!!

(No apologies for shouting.)

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Serotonin and depression

This post is an attempt at summarising and explaining a paper called 5-HT and depression: is the glass half full? Authored by Trevor Sharp and Philip J. Cowen which was published in Current Opinion in Pharmacology, 2011 volume 11 pages 45–51.

The theory that abnormally low levels of the neurotransmitter serotonin (also called 5-hydroxytryptamine, 5-HT) can cause depression is now 50 years old.

The theory arose when it was noticed that depressed patients had low serotonin levels in cerebrospinal fluid, and also that the first effective antidepressant drugs had the effect of increasing the amount of serotonin in the gap between neurons (the synaptic cleft). Since then the old tricyclic antidepressants have been replaced with medications that more accurately target serotonin, the ‘selective serotonin re-uptake inhibitors’ (SSRIs) which have fewer adverse effects and tend to be more effective at relieving depression symptoms.

Despite the progress since 1967, up to half of the patients prescribed antidepressants do not get enough relief from their symptoms, and pharmacologists still don’t clearly understand how changes in serotonin translate to altered mood.

That 5-HT (serotonin) is associated with mood and depression has been shown by pharmacological studies and also positron emission tomography (PET) studies looking at the distribution of 5-HT receptors in the brains of depressed patients. Other studies have shown that artificially restricting dietary intake of the amino L-tryptophan can cause a return of depression symptoms in patients with a history of depression. This is significant because L-tryptophan is the precursor (chemical building block) of 5-HT. Similar L-tryptophan depletion in people who have a high family incidence of depression but themselves have not had depression caused a less severe lowering of mood.

Genetic components

Depression does run in families, with a moderate to high heritability (heritability is a measure of how likely a trait is inherited, low means less likely and high indicates it is more likely to be inherited in a population).

One particular gene, slc6a4, which codes for the 5-HT transporter protein, has been well studied. Levels of the 5-HT transporter can vary by up to sevenfold within the general population. Individuals with low levels of this 5-HT transporter have increased risk of depression when associated with stressful life events. The region of this gene where it is regulated (i.e., ‘the volume control’) is rich in methylation sites which can result in semi-permanent changes to gene expression as a result of environmental influences (such as a stressed or depressed mother during pregnancy, stressful events, childhood trauma).

Neuronal Repair

Current thinking is that increased synaptic 5-HT activates a downstream gene programme that leads to enhanced neuronal plasticity which has failed because of the adverse effects of stress and other environmental and genetic factors.

In effect, some sort of stress derails the ongoing repair and maintenance of brain ‘circuitry’ which can be overcome by bumping up serotonin levels in neurons.

This idea of serotonin enabling improved neuronal plasticity in depressed patients dovetails nicely with ideas of how psychological treatments (such as counselling, CBT, DBT) function to help treat depression. Psychotherapists help a patient to reframe situations and learn more positive ways to view situations. With increased serotonin levels enabling neural repair and realignment of neural pathways, learning is facilitated and so the therapy and drug treatment work together.

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Counting decimal places

As a biochemist I have become quite accustomed to doing unit conversions in my head and working in scientific notation. But we all occasionally have to stop and count decimal places to get it right. The owner of this calculator (a student left it in one of our teaching labs) obviously has particular problems with this!

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Let the bugs live

I read an interesting, and worrying, article today from the Guardian:

Warning of ‘ecological Armageddon’ after dramatic plunge in insect numbers.

It discussed the results of a longitudinal study surveying the biomass of flying insects in German nature reserves over the period from 1989 to 2016. Overall, the study found a 76% decline in the biomass of flying insects.

The authors of the published paper suggest that pesticide use and climate change are likely to be significant factors contributing to the loss of insects.

Some might react with gladness – the fewer annoying bugs the better. However, insects are a crucial part of the food chain and both plants and animals depend upon them to survive so rapid loss of insects over such a relatively short period is extremely concerning.

Another way to dismiss the relevance of this study to us in New Zealand would be to argue that it was performed in Europe which is considerably more developed than here and possibly more polluted. Yet we are even more dependant on agriculture than Germany so a similar decline in insect population here could have a massive impact on our economy. We also use large amounts of pesticides here too, and history shows that New Zealand’s ecosystems are sensitive to changes like this.

I have no idea if similar studies have been conducted in New Zealand, though I’m now curious to find out. The implications of a global decline in insects are huge, many of us may dislike bugs but for life on earth to continue we do need them.