All posts by Kate Timms

Kate is a PhD student who previously studied Biomedical Sciences (because she couldn’t decide what she wanted to specialise in) and Maternal and Fetal Health (because eventually she did decide). When not working in a science lab at the University of Manchester until an unseemly hour, she can usually be found watching women’s football (usually also at an unseemly hour). She also has a peculiar habit of trying to make other people watch also her favourite sport. Seriously, have you ever watched a game of women’s football?

Trees rings show that today’s summers are warmest ever

We all like to have a good moan about the weather. Our grandparents tell us that summers are never as sunny as they used to be in the good old days. Well, according to research published today, it turns out that summers aren’t the same temperature today as they were when our grandparents were young. They’re warmer.

A study published today by 45 scientists from 13 countries uses evidence from tree-rings to put our modern European summer temperatures into the context of the last 2,000 years.

round tree ringsEach year a tree lays down a ‘ring’ of new wood, which creates the ring pattern we’re all familiar with (image right). Rings alter in colour and density depending on the year’s growing conditions – a fast growing tree lays down lighter and less dense rings than a slow growing one.  By comparing recent tree rings both to temperatures recorded by today’s thermometers and to ancient tree rings, scientists could deduce the temperatures of summers going back to more than 2,000 years

It turns out that temperatures over the last two millennia were more variable than we first thought (see graph). Summers were relatively balmy in Roman times (good weather for togas), followed by a cooling period that continued until medieval times. Shortly after, Europe entered a so called ‘little Ice Age’, which continued from the 1300s all the way through to the apparently chilly reign of Queen Victoria in the 19th century.

 

bhm_30yInst_gradients_nobox European summer temperature variations 137 BCE to 2003 CE and associated uncertainties. Copyright: CC BY-SA 4.0 J.P. Werner/EuroMed2k Members.

 

When these variations are compared to our rapidly warming modern temperatures, it becomes clear that what we’re experiencing today now lies outside of this natural variability. It shows us that while some change in temperature is normal over time, the kind of big changes we are now experiencing is anything but natural. The coordinator of the study, Professor Jürg Luterbacher from the University of Giessen in Germany, says that we can use this new information to help predict the impacts of future global warming.

Based on this latest research, it looks like extremes in weather are set to continue and the summers will be getting warmer. Hopefully, with studies like this our ability to predict these extremes will improve, helping is to cope with what’s to come. I can’t help but wonder, though, what the people of a thousand years from now will think when they see the tree rings being made today. By then, even our extreme weather may seem like ‘the good old days’. Or maybe we’ll have found a way to save our ailing planet – touch wood.

 

Photo Credits: Paul Schadler and Paul Filmer via Flickr Creative Commons.

Article by Kate Timms

January 29, 2016

Kate Timms

Kate is a PhD student who previously studied Biomedical Sciences (because she couldn’t decide what she wanted to specialise in) and Maternal and Fetal Health (because eventually she did decide). When not working in a science lab at the University of Manchester until an unseemly hour, she can usually be found watching women’s football (usually also at an unseemly hour). She also has a peculiar habit of trying to make other people watch also her favourite sport. Seriously, have you ever watched a game of women’s football?


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Should I run cold water over lettuce before I eat it?

Q. How many bacteria are actually displaced by this activity? Or am I just imagining that I am making my food safe to eat?

I’ll be honest with you, I rarely give my salad leaves a rinse in tap water before eating it. Most of the lettuce we buy in the shops today has already been washed before it reaches the shelves anyway, making us think that it is ready to eat. However, ‘ready washed’ doesn’t always mean ‘clean’…

Aquaponic LettuceIn her book Swallow This: Serving Up The Food Industry’s Darkest Secrets, Joanna Blythman brings to light the unpalatable truth that ‘ready washed’ salad leaves are likely to have been washed in chlorine-containing water – that could be up to 8 hours old. Chlorine is effective at killing some (but definitely not all) bacteria, but when it’s 8 hours old, the chlorinated water’s bug-killing abilities could be seriously reduced.

It gets worse though. Bacteria thrive in wet, humid conditions and if you’ve ever eaten pre-packaged salad then you’ll know just how damp it can get inside those bags (especially if you don’t eat them right away). Even at 4oC – the temperature that your fridge should be set to – bacteria can survive and flourish. Just dig out that forgotten bag of greens tucked away at the back of your fridge and you’ll see (and smell) what I mean.

But does this mean that pre-washed lettuce is dangerous? Well, not really.

As long as you wash all of your lettuce (including the kind that helpfully tells you that it’s already been washed), you shouldn’t have a problem. Research shows that washing lettuce with tap water removes more than 90% of bacteria – providing you wash it thoroughly, that is.  According to a study by Professor Martin Adams of the University of Surrey, ‘thoroughly’ means plonking the chopped up lettuce into some tap water and swishing it about for 5 minutes. This might sound a little extreme, but it seems to do the job.  At least for most bacteria.

There will always be some bacteria that aren’t removed by washing. Some bacteria can cling onto the surface of the lettuce incredibly well – especially if they are living in a community of bacteria called a biofilm. Some bacteria might also be hiding deep inside the lettuce and so removing these bacteria by washing it in cold tap water is pretty much impossible.

Salmonella Bacteria

Fret not though, because munching down on some micro-organisms may not be all that bad. The well-established ‘Hygiene Hypothesis’ states that if we’re not exposed to enough bacteria and infectious diseases, especially in early life, then we’re more likely to develop allergies. So rather than aiming to eat perfectly sterile food, it’s more important to make sure that food hasn’t been contaminated with bacteria that could do us serious harm – like some types of E. coli and Salmonella. And sadly, the Food Standards Agency say that washing is not very good at removing pathogenic bacteria from fresh produce. So however well you wash your lettuce, there’s no absolute guarantee that you’re making it safe to eat.

Mercifully, outbreaks of illness from eating lettuce and other fresh produce are pretty rare, accounting for less than 1 in 10 of all food poisoning cases in the UK. Half of all food poisoning cases are traced back to poultry and food producers nowadays do a fairly good job of keeping their crops clean of the nastier kinds of bacteria. Your chance of dying from food poisoning by Salmonella is 1 in 5.1 million per year in the UK. You’re far more likely to die by falling off a ladder (1 in 1.2 million) or drowning in the bath (1 in 2.7 million).

So does washing lettuce make a difference? Yes it does. Is it perfect at cleaning off all the nasties? Not really. But should you get worried about it? Probably not.

What you should be worrying about is whether you’re really willing to risk your life by choosing a bath over a shower tonight. Or eating that chicken for dinner. Maybe you should just play it safe and shower with your lettuce instead.

Photo Credits: Megan and NIAID via Flickr Creative Commons

Article by Kate Timms

January 28, 2016

Kate Timms

Kate is a PhD student who previously studied Biomedical Sciences (because she couldn’t decide what she wanted to specialise in) and Maternal and Fetal Health (because eventually she did decide). When not working in a science lab at the University of Manchester until an unseemly hour, she can usually be found watching women’s football (usually also at an unseemly hour). She also has a peculiar habit of trying to make other people watch also her favourite sport. Seriously, have you ever watched a game of women’s football?


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Why does an itch move when I scratch it?

Many people complain about ‘moving itches’, but I had never noticed it before. So, I waited for an itch. Surely enough, one came along almost straight away and I diligently scratched it. It moved.

At first, this might seem like the power of suggestion – perhaps I felt it because I was told it would happen? But make no mistake, moving itches are very real.

Something irritates our skin, making it itch. When we feel the itch, we scratch it. It’s very satisfying, but our skin isn’t quite so keen on it. Scratching an itch damages the skin and causes pain. Not a lot, I’ll grant you, but enough that our brain doesn’t like it. It responds by releasing a chemical known as serotonin to make us feel better. Also called ‘the feel good hormone’, it makes us feel happy. It also turns out that serotonin itself also makes us itch.

26/365 Wound byTraci LawsonResearchers have found that mice with no serotonin scratch their itches less. When these mice are given serotonin, they scratch more. This is because there are some ‘itch signal’ nerves in our spinal cord that have both ‘itch receptors’ (the GRP receptor) and ‘serotonin receptors’ (the 5-HT1A receptor) on them. When serotonin binds to the 5-HT1A receptors on these nerves, ‘the itch signal’ is sent out to our brain, making us feel an itch. This surge in serotonin makes us itch more, either in the same place as before or somewhere else.

It’s likely that the ‘moved’ itch was already there but was too minor for us to notice. When serotonin gets involved, the itch gets itchier and so we scratch it. Which releases more serotonin, making us itch even more. It’s a vicious cycle that’s pretty hard to break.

So, next time you feel an itch, maybe you should just try to ignore it. Which, as I am discovering, is easier said than done.

Answer by Kate Timms

 

Zhao, Zhong-Qiu, et al. (2014). Descending Control of Itch Transmission by the Serotonergic System via 5-HT1A-Facilitated GRP-GRPR Signaling. Neuron, 84(4), 821-834

Photo Credits: Michael Verhoef and Traci Lawson via Flickr Creative Commons

Article by Kate Timms

January 13, 2016

Kate Timms

Kate is a PhD student who previously studied Biomedical Sciences (because she couldn’t decide what she wanted to specialise in) and Maternal and Fetal Health (because eventually she did decide). When not working in a science lab at the University of Manchester until an unseemly hour, she can usually be found watching women’s football (usually also at an unseemly hour). She also has a peculiar habit of trying to make other people watch also her favourite sport. Seriously, have you ever watched a game of women’s football?


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