GLT 303
THIRD & FOURTH LECTURE
AUTOCLAVE
In Autoclaving, pressure is used to produce high temperature
steam. The temperature of a saturated is 100oC. When water boils,
temperature increases with pressure. Autoclaving at 121oC for 15-20
minutes is required for proper sterilization. Both the temperature and the
holding time must be correct to obtain sterilization. All the air in the
autoclave must be removed while sterilizing to avoid “dry heat”. A mixture of
hot air and steam will not sterilize, therefore, before the commencement of
sterilization, sufficient of sterilization, sufficient time must be allowed for
the saturated steam to permeate the entire load and heat transfer to occur.
Sterilization can be done at 115oC for 30 minutes at 10lb or 121oC
for 20 minutes at 10lb or 121oC for 15 minutes at 15lb.
Reasons
For Using Saturated Steam During Autoclave
1.
To avoid dry heat.
2.
To avoid superheated steam
Autoclave
uses the principle of steam under pressure.
Mode of Operation – Steps
1.
Add correct amount of water to the autoclave as
direct by the manufacturer user manual.
2.
When loading the autoclave, leave sufficient
space between the articles for steam to circulate or permeate freely.
3.
Do not allow the article to touch the side of
the chamber or stand in the water.
4.
Use a tray or a wire stand at the bottom of the
chamber.
5.
Place a control TST (Time, Steam, Temperature)
indicator strip, in the centre of the __________
6.
Cover the lid of the autoclave
7.
Open the air outlet
8.
Switch the power on
9.
Allow the correct length of time for all the air
to be expelled.
10. Close
the air outlet. This will allow the pressure to rise with the increasing
temperature.
11. When
the required pressure/temperature is reached as shownon the pressure guage,
start timing.
12. At the
end of sterilization, turn off equipment and allow it to cool naturally/open
the value to let the steam expel.
13. When
the temperature gauge reaches 80oC and the pressure reaches 0lb, the
cover can be removed.
14. Check
the TST indicator strip to ensure that sterilization is complete.
CARE
AND MAINTENANCE
1.
Read carefully the manufacturers user manual and
prepare a stock record covering the use, care and maintenance of the equipment.
2.
Hold in store extra lid, value or any other part
of the equipment.
3.
Clean the inside of the autoclave after usage
and make sure the values are not blocked.
4.
Check regularly for the signs of wear and tear.
5.
Check for the electrical flux.
6.
Do not use the falp when it is faulty obtain the
help from engineer when it is faulty.
7.
Use TST indicator strip to check the performance
of the autoclave.
AUTORADIOGRAPHY
Autoradiography is a technique using X-ray film to visualize
molecules or fragment of molecules that have been radioactively labelled. The
photographic plate present in the equipment is used to expose radioactive
emission from the subject being studied. The subject is usually biology
specimen or human body part.
Radiography
is the use of radioactive materials or X-rays to produce an image. Using X-rays
to bombard a subject while exposing a photographic plate or film to the X-rays
is the most common for this type of images.
Autoradiography
produces a similar image but relies on emission of alpha and beta particles and
the gamma rays are released by the decay of radioactive substances with the
subject rather than outside source.
RADIO
– ISOTPES
The mass of atomic nuclei can vary slightly for a particular
element although the number of electrons remains constant. The nuclei of
radioactive isotopes are unstable and they disintegrate to produce new atoms
and at the same time give off radiation.
Naturally
occurring radioisotopes are rare because of their instability but radioactive
atoms can be produced by the bombardment of stable nuclei with high energy.
Disintegration
can be detected in three ways;
1.
Electrical
2.
Scintillation
3.
Autoradiography
1.
Electrical:
this
depend on the production of ion pair by emitted radiation to give an electrical signal that can be applied and registered using Geiger counter, Ionization
Centre and Gas.
2.
Scintillation:
some
materials have the property of absorbing energy and re-emitting this in the
form of visible light. In this some flashes are converted into electrical
impulses.
3.
Autoradiography:
this
differs from pulse-counting technique in several ways. The crystal of silver
halide in the photographic emission is an independent detector insulated from
the rest of the emission.
TYPES
OF RADIOACTIVE EXPERIMENT
1.
In Vivo experiment
2.
In Vitro experiment
COMPONENT
OF AUTORADIOGRAPHIC FILM
1.
Upper protective coats.
2.
A layer of gelatin that contains silver halide.
3.
Film base usually made from flexible polymer.
4.
Anti-halation backing to prevent light from
reflecting back into the emission.
Block diagram of autoradiography...
USES
OF AUTORADIOGRAPHY
1.
It is used to study R.N.A and D.N.A as well as
the phase of cell development and function.
2.
It can be used to isolate partial sequence of
R.N.A and D.N.A for study especially in viruses.
3.
Doctor also use it to detect, diagnose and
devise treatment strategies of various types of radioactive poisoning by
determining which tissue have absorb radioactive materials.
4.
Autoradiography can be used to detect and
measure semi-quantitatively the radioactive materials in almost any object that
can be placed in contact with film of photographic emulsion in some form.
However, in biological research the object may be:
i.
A whole plant or animal that can be flattened
against a fume.
ii.
The cut surface of a plant or animal or one of
its organs
iii.
The section of tissue or cells
iv.
Surface films produced by spreading on water the
protein mono layer containing DNA or RNA that are pick up in grids for electron
microscopy.
v.
Sheet of paper or other materials on which
radioactive substances have been separated by chromatography or
electrophoresis.
vi.
A crymamide gels in which DNA, RNA or proteins
have been separated by electrophoresis.
TYPES
OF PHOTOGRAPHIC DETECTION SYSTEM
1.
Stripping film.
1.
Liquid photographic emulsion.
1.
Stripping
film: consist of an even layer of photographic emulsion on a
supportive gelatin membrane (e.g. Kodak Ario) it is floated on water and then
wrapped around the slide and form very close contact as it dries. This was once
widely used but it is now no longer made. It has a major advantage of uniform
thickness but the disadvantage is that supporting membrane prevents counter
staining of the section and therefore the tissue block must be pre-stained before
section are quoted.
2.
Liquid
Photographic emulsion: this is the method routinely used today,
it is simpler and quicker to drew but the layer of liquid emulsion (e.g. Kodak
Mb2) can be slightly un-even in thickness as it follows down to the bottom of
the slides as it is for most purpose.
OVEN
An oven is a
thermally insulated closed chamber used for heating, baking, drying of a substance
and can also perform miserlenous industrial purposes. The first oven was a simple
container placed over a fire to bake family meal and we have May types which includes;
Gas, Electric, Hot air, Microwave, Infrared.
The Gas oven
works when natural gas is ignited to produce heat, while the electric oven
works on the same principle but the electric wire provides the heat.
TYPES
OF OVEN
1.
Earth oven.
2.
Ceramic oven.
3.
Gas oven.
4.
Mansoury oven.
5.
Microwave oven.
1.
Earth
Oven: this is a pit dug into the ground and then heated usually by
rocks or smoldering debrise. It is the most common thing the iconologist look
for at an anthropological dig as they are one of the key indicators of human
civilization and static society.
2.
Ceramic
oven: this is an oven constructed of clay or any other ceramic
materials and takes different forms depending on the culture; the Indians call
it tandoor has been used for cooking.
3.
Gas oven:
this
is by invention, gas stores were usually used in ancient times not until modern
gas came notable improvement to the gas stores which includes the addition of
thermostat which assists in temperature regulation. Also an enamel quoting was
added to the production of gas stores and ovens in order to help with easier
cleaning.
INCUBATORS
Incubators are
used for culturing or used to grow culture and works under dry heat, low
temperature. Incubation at controlled temperature is required for
bacteriological culture, hematological culture, serological culture, and
microbiological analysis. Micro-organisms require incubations at temperature,
humidity and gaseous atmosphere, suited for their metabolism.
USES
AND CARE OF AN INCUBATOR
1.
Read and adhere to manufacturer’s manual and
preparing stock record card.
2.
Make sure the equipment is positioned on a level
surface and that none of the ventilation openings are obstructed.
3.
If the incubator does not have a temperature
display, insert a thermometer on the vent hole through the roof of the
incubator.
4.
Adjust the thermostat dial until the thermometer
shows the correct reading e.g. 35oC for routing incubation of bacteriological
culture.
5.
Before incubating cultures, check the
temperature.
6.
Clean the incubator regularly.
7.
Make sure it is first disconnected from the
power source before cleaning.
8.
Every 3-6 months (depending on the age and
condition of the equipment) check the incubator and flex and signs of wares and
tears.
9.
At the point/time of purchase it is advisable to
buy spare parts of the thermostat, thermometer or any replaceable part.
FACTORS
TO CONSIDER BEFORE PURCHASE BOTH OF INCUBATORS OR OVEN
1.
Consider the price.
2.
Availability of the part.
3.
Reputation of the seller.
4.
It should have inner glass to see the inner
content while working.
5.
The one that has regulator or indication should
be bought.
6.
The one that has time range should be purchased.
THINGS INCUBATORS AND OVENS
HAVE IN COMMON
1.
They both use electricity
2.
They both have switch
3.
They both have shelves
4.
They both have inner glasses
BALANCES
They are equipment used to compare a
measured weight with a known standard.
To prepare essential reagent, stains and
culture media, a balance is required that weighs accurately and precisely
within the range and sensitivity required.
TYPES
OF BALANCES
1.
Mechanical
balance: these include the single pan, trip and tungsten. They do not
require any means of electricity of battery power. They are less expensive than
electronic sensitivity balance and are widely available.
2.
Electronic
balance: a wide range of top-loading and analytical electronical
balance is available, they are single pan that use an electromagnetic force
instead of weight, and they are operated by means of electricity and often from
batteries. They weigh rapidly and reboot which allows the weight of weighing
vessels to be zero.
USES
AND CARE
1.
Consider the manufacturer’s manual.
2.
Consider the stock.
3.
Handle with care.
4.
Position the equipment on a firm bench away from
vibration, draught and direct sunlight.
5.
Ensure the balance is levelled, adjusting if necessary;
the screw on which it stands and check the spirit level or plumbing that is at the
Centre.
6.
Before weighing,
zero the balance as directed by the manufacturer.
7.
Weigh chemicals at room temperature.
8.
Never weigh on the weighing pan and place the
weighing vessel in the centre of the pan.
9.
When adding or removing the sample from the
container, remove from the pan to avoid spilling on the balance pan.
10. After completing the weighing, return the
balance to zero and use a small brush to wipe away substance on the pan.
11. Keep the balance clean and cover when not in
use.
12. Check the
accuracy of the balance by re-weighing a standard known weight.
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