Specimen Nr. 04B

Specimen:

Thymus (Rat)

Staining:

Peroxidase, anti-peroxidase technique, apoptosis

Magnification:

150x

Important structures :

1.	Septum
2.	Cortex
3.	Medulla

Mit der TUNEL-Technik sind DNA-Strangbrüche in braun dargestellt. Sie sind immer dann nachweisbar, wenn eine Zelle apoptotisch wird, also programmierten Selbstmord begeht. In der Rinde des Thymus sind mehr apoptotische Lymphozyten als im Mark.

Legende:

	Septum
	Cortex
	Medulla

Localisation of organs of immune-lymphatic system[we]

1.	Pharyngeal tonsil
2.	Palatine tonsil
3.	Lymph node
4.	Lymphatic vessels

5.	Spleen
6.	Peyer's patches
7.	Thymus

Immunohistochemestry

Immunohistochemistry is used to confirm the presence of or to identify certain structures or substances in tissue sections which cannot be identified with conventional staining methods. Such structures include: cells, enzymes, hormones, macromolecules like nucleic acids and polysaccharides. The basis of immunohistochemical staining techniques is the antigen-antibody reaction. This method makes it possible to differentiate, for example, various cells in a tissue section according to their different metabolic products or surfaces. Either the metabolic product or a certain surface component serves as the antigen. In the first step, the antigen reacts with a specific antibody. The resulting antigen-antibody complex is invisible. Therefore, in a further step a second antibody bound to an adjuvant is added and binds to the initial antibody (so-called sandwich procedure). The bound adjuvant makes the antigen-antibody complex visible under the microscope and identifies the sought structure. Adjuvants are:

fluorescent dyes:
fluoresce by stimulation under UV light
enzymes:
catalyze a definite dye reaction
particular markers:
The immune complexes can be made visible with, e.g. bound gold particles, both in direct light and under the electron microscope.
radionuclids:
The substance sought is identified by blackening a photographic plate or an applied photo film.

Combination with further dyes or staining techniques:

hemalaun
dye for staining cell nuclei
result: Cell nuclei turn an intense blue.

Die Rinde des Thymus enthält etwa 1% apoptotische Zellen. Da eine apoptotische Zelle weniger als eine Stunde positiv markiert wird, sterben pro Tag mindestens 25% Lymphozyten der Thymusrinde. Diese Zahl reicht aus, um den Tod von über 95% der im Thymus gebildeten Lymphozyten zu erklären, da nur wenig mehr als 25% Lymphozyten pro Tag neu gebildet werden.

Magnification:

150x

Magnification:

150x

HistoNet2000 - Help

1. Organization of the screen surface

Right side: histologic specimen
Left side: information about the specimen (above) and general program functions (below)

2.Histologic specimen

Pull the mouse across the histologic specimen for training purposes. A small square with exclamation marks (dynamic labels) will appear where there is an important structure. You should then decide what structure this could be. To check your result, simply click the appropriate square, and the correct label will appear. The option “marked” allows you to see all labels for all structures simultaneously. These can be removed by clicking “unmarked”. This reactivates the dynamic labels.

3. Complementary information

Info: general information about the specimen, as well as a list of the dynamic labels
Drawing: schematic drawing of the specimen
Staining: information about the staining method for this specimen
Knowledge: short texts with basic histologic information, presently deactivated

4. General Program Functions

Home: returns you to the “start” page
Tutor: how to contact the HistoNet Team
Help: Instructions for Use appear
Exit: closes down the HistoNet program
Boxes: goes back to the other specimen of a topic
VM: provides virtual microscopy

We hope you will enjoy working with HistoNet2000 and learn a lot from it!