Epidemiology - Bias

"Define and specifically discuss the different types of bias within the context of scientific research and their possible consequences in the nutrition field"

Wiki: In science and engineering, bias is a systematic error.  Statistical bias results from an unfair sampling of a population, or from an estimation process that does not give accurate results on average.

Pre-trial bias = Flawed study design, Selection bias, channelling bias
Bias during trial = Interviewer bias, Recall bias, transfer bias, misclassification of exposure or outcome, performance bias, chronology bias
Bias after trial = Citation bias, confounding


How to avoid bias:
Pre-trail bias

Flawed study designs - clearly define risk and outcome. Standardize and blind data collection.

Selection bias - Select patients using rigorous criteria to avoid confounding results. Chose patients from the same population. Avoid selection bias as outcome is unknown at time of enrolment.

Channeling bias - Assign patients to study cohorts using rigorous criteria

Bias during trial

Interviewer bias - Blind interviewer to exposure status and other factors. Standarize interviewers interaction with patient.
Chronology bias - Avoid using historic controls.

#examgate

Group chat:

Woah that was amazing guys

Yeah thank god. It's over and it was good.

What? Are you guys kidding right?

Anna and I were taking our exams in another room.  The other 4 of our group were in the main exam hall.
All in the hall were told to cross out the last 10 questions and were given another piece of paper which was totally nothing we had revised.

Anna and I were just given the usual paper.  Cutting a very long story short, the head of science was rude, defensive and not at all apologetic for this mistake.  Sadly for Anna and I (but fairly) all questions were erased.

The entire thing has all been a nightmare.  I'm getting sick of all this.

Revision: Fertilisation

Please bear in mind these are my revision notes and I can't quite promise their accuracy.  Do your own research too! Typing these out will help me remember as we are heading into a seen exam this afternoon!


Question: Describe the cellular and molecular events that occur during fertilisation

Approximately 200million spermatozoa are released during ejaculation in intercourse, travelling through the vagina and swimming through the cervix propelled by whip like motions of the flagella.  After which  muscular contractions of the uterus direct them to the fallopian tubes.
This process usually takes between 30 minutes and 2 hours.  Around 200 spermatozoa will reach the oocyte in the fallopian tube.  Only one will fertilise.

Capacitation and the acrosomal reaction must take place before fertilisation can begin.  Secretions from he uterus wall destabilise the plasma membrane surrounding the head of the seprm resulting in the membrane becoming more fluid which helps prepare the sperm for the events of fertilisation.  The sperm become hyperactive as they move through the corona radiata and come into contact with the zonae pellucida.  Here, specific receptor proteins called ZP3 triggers the acrosomal reaction during which the enzymatic contents of the acrosome are released.  These enzymes digest a path through the zonae pellucida into the perivitelline space  and reach the plasma membrane of  the secondary oocyte.  Here the fusion takes place.

To ensure only one sperm fuses a fast and slow block is released preventing any further ZP3 being released and therefore preventing polyspermy.  The slow block is depolarisation and fast block sees
 a wave of intracellular calcium being released causing small cortical granules beneath the oocyte membrane to release their contents.  Thus rendering ZP3 inactive making the zonae pellucid impermeable.

Upon sperm entering, the oocyte undergoes Meiosis 2 and further develops into a female pronucleus. During this time the sperm develops into male pronucleus.  The two pronuclei fuse to form one single diploid nucleus known as a zygote.

Revision - Main characteristic of Viruses.

NB this is my own revision and I cannot promise accuracy - do research.

Question:
a)  Discuss in depth the main characteristics of viruses

Viruses are not classed as living things as they cannot replicate without a host.  They do not have a metabolism.
Viruses spread using cells.
They have a protein coat called a capsid.
Viruses are very small, much smaller than bacteria.
They are difficult to treat.

b) Give a detailed account of the main events involved in a typical virus life cycle

A virus enters the body and locates a host cell.  As it fuses, it uses the protein coat to enter the cell.  Here,  it enters either a lytic cycle or a lysogenic cycle .  Nucleic acid will be used to reform DNA/RNA and change the genetic material of the cell.
The lytic cycle then sees the cell erupt making copies of the other cells.  Leaving holes in the cell membrane gives ease to apoptosis of the cell as it cannot survive without the membrane.
The lysogenic cycle uses DNA to hide in cells until immune comprimisation occurs.

c)  List factors contributing to viral pathogenicity and to the nature and severity of viral diseases.

Pathogenicity refers to the ability of an organism to cause disease (i.e. harm the host).  This ability represents a genetic component of the pathogen and the damage done to the host is a property of the host-pathogen reactions.

Natural killer cells are lymphocytes, they recognise this virus and kill.
The severity of viral diseases is dictated by the immune response. In several immune deficiency diseases including AIDS NK cell function is abnormal.
NK cells binds to cell and releases toxins which produces holes int he target cells membrane creating apoptosis.
NK cells may also contribute to immunoregulation by recreating high levels of influential lymphokines.

Revision: Fertilisation

Q1B - please see previous blog post for Q1A - Remember these are my revision notes and you must do your own research for accuracy.

Question:  Outline the experimental evidence for the role of one molecule in fertilisation

Baibakov et al found human sperm bind to Homo sapiens zonae pellucida but not to those of non-human primates.
Human sperm only bind to zonae pellucid with contained human ZP2.  Recognition of fertilisation within species is dependant on a N-terminal domain of ZP2.  After fertilisation degradation takes place of N-terminal ZP2 to block polyspermy.

Failing exams

Two results are in and I failed.

Metabolism and Disease
Immunology.

Immunology I actually passed the exam but the phase test earlier in the year I only got 5% and it dragged me down.

I don't know what I'm thinking.  Could I do any better? I did my very best and was convinced I smashed it. Something is wrong here as so many of us didn't pass...

Promise of 2017 - Cardiology

The promise of a new year.  2017.  As the media, the public and the laymen happily rang out 2016 with the wearing of black as we said farewell to the biology of so many talented individuals, we started 2017 with hope.

Everyone being sure 2017 has got to be better than its predecessor. 

My family sighed with relief too as we rang in the new year (me in my nightwear in the middle of a dairy farm in Wales).  Last year was full of worry and tragedy.  Yet we made it through.  Stronger as  a family than ever.  My knowledge of the brain stem, strokes and death far more inscribed in my brain than before as we celebrated the life of my 74 year old father.

We miss him, of course.

With those words of "Mum will live to 100" coming back to haunt me, we rushed her into casualty with a pulse of 45,  stars in her eyes and feeling as though she would lose consciousness at any minute.  

"Heart block" the paramedic had explained.  

The second ECG at hospital showed progession from 1st degree to 2nd degree as they took Mums blood from her bruised vein.  Tropotin was through the roof.  This is an enzyme released by damaged heart cells.  This showed us mum had an MI.  A heart attack.

Her care was fantastic.  Right away, fragmin in her belly, aspirin down her throat and canulas a plenty.  Recussitation trolley all day long gave her a 'bum ache' as she laughed along with the nurses.  This was very serious.  Yet her spirit remained unscathed as I quoted her on Facebook so her friends could see her sense of humour was definitely not harmed.  

A week in intensive care,  a stent in the Right Coronary Artery which was 99% blocked, left one showing a few signs,

echocardiogram showing 'significant damage' to her heart muscle and constant monitoring showing me that she was missing beats.  They called them Blips to Mum.  That was all she needed to know.  I researched and researched and took photos of her trace to send to my contacts in the know.  Turns out their diagnosis via mobile phone was right, Mobitz 2.  

Making the most of Mum,  having her home with us, I was immediately thankful.  Until I realised the sounds of Phil and Holly presenting on This Morning right behind my desk was very distracting.  

Can I cope?  Can I continue my studies, work and look after mum, Scott and the twins?  Of course I can.  I can do anything I put my mind to!

Up against it, yes.  

Not beaten.