Thursday, 25 November 2021

Pigment protects

The skin is the largest organ of the human body. The skin consists of three layers. The top layer is formed by the epidermis. The middle layer is called the dermis. The bottom layer is the subcutaneous connective tissue. The epidermis consists mainly of special skin cells called the keratinocytes. The keratinocytes are formed in the lower layer (the basal layer) and slowly slide upwards from there. Gradually they transfer to a dead keratinized cell layer, the horny layer, where the cells lie loosely against each other.

Melanocytes are present in the epidermis, in addition to the keratinocytes. Melanocytes are pigment cells that lie between the cells of the basal cell layer and make the pigment grains that are transferred via offshoots to the keratinocytes. The pigment of the pigment granules, the melanin, determines to a large extent the color of the skin and protects us from sunlight. The more pigment grains, the darker the skin. Pigment is a brown dye that is produced by the pigment cells in the lower layer of the epidermis. Pigment cells lay therefore relatively superficial in the skin. In the pigment cell, the pigment is packaged in pigment granules, and thus delivered to the upper epidermal cells. Only when the pigment is in the epidermal cells the skin is visibly pigmented.

The functions of pigment cells are besides determining the skin color also protecting the skin against harmful ultraviolet (UV) rays. Under the influence of UV radiation, the number of active pigment cells and pigment production increases. The result is a brown discoloration of the skin.

With thanks to Dr. Eddie Wisse and Frank van Campen, members of the Royal Antwerp Society for Micrography.
Prepared slide by Lieder

Tuesday, 23 November 2021

Snails: Powerhouses

Snails are the only mollusks that can live on land. As many as 60,000 to 75,000 species are known in the world. Snails are also called gastropods. This is because the muscles on the abdomen (bottom of the snail) are responsible for the movement. Most snails are hermaphrodite, which means that they have both male and female sexual organs. Some snails are even solitary and can reproduce without needing another snail!

Believe it or not, but a snail has more teeth than a shark! A snail can have more than 25,000 teeth and sharks "only" have 3,000. The snail hides all these small teeth on its tongue (radula)_ and scrapes small pieces off the leaves that it eats. Ever wondered why there are so many holes in the leaves of your plants? A snail can eat up to half its own body weight in one day! It does not matter much what snails eat. They prefer to eat only the soft part of the plant, but when there is a long drought, they can take a bite from your newspaper if they can't find anything else. They are not picky.

Thursday, 11 November 2021

Artery from another perspective

The preparation of the artery shown in both images is of unknown origin and the staining method is unknown as well.

A fluorescence image of an artery tissue as shown here is not usual. The preparation is more or less evenly green fluorescent colored, because the dye used has attached itself to the structural parts of the preparation. We see a fluorescence color image with details as you might encounter in bright field microscopy with dyes such as e.g. toluidine blue. Such dyes show more or less the same details in the preparation with ordinary bright field microscopy as is shown in the first image.

As mentioned before, visualizing a histological specimen completely by using a fluorescent substance is unusual, because here you apply only one color that shows no specific adhesion, except for proteins, because e.g. fat is uncolored in this preparation. With a normal hematoxylin and eosin staining you have more differentiation, namely in the cell core (DNA, dark blue) and proteins, cytoplasm (pink)

In histology, fluorescence is mainly used after a fluorescent substance has been chemically attached to a specific component present in the tissue.

On the fluorescent image of the preparation the parts of an artery can also be seen. The lumen is filled with green colored red blood cells, then there is a very thin (barely visible) layer of endothelium, the meandering lamina elastica interna (clearly visible) a layer of smooth muscle, the thinner lamina elastica externa (clearly visible), the adventitia (connective  tissue) that turns into adipose (fat) tissue. 

Thursday, 21 October 2021

Thousands of small lenses work together

Seen from the front, the head of the honeybee has a triangular shape, the head of the drone it is more round. On the head are the eyes, antennae and mouth parts. Important glands are located in the head and the main center of the nervous system: a nerve bud that serves as a brain.

Friday, 15 October 2021

A switching station

Ganglia are part of the peripheral nervous system. The peripheral nervous system includes all nerves outside the central nervous system (bundles of long nerve shoots with supporting cells) and small centers of nerve cells the ganglia.

A ganglion is a combination of mainly cell bodies (ganglion cells) with the nucleus of the nerve cell surrounded by cytoplasm without further shoots. This cell body with the nucleus as its center forms the metabolic center of the cell and is sensitive to stimuli. Ganglia function as switching stations for nerve impulses.

Wednesday, 6 October 2021

A pest from Africa

The southern green stinkbug (Nezara viridula) is a relatively new pest that originates from Ethiopia. The pest has a large number of host plants, but in horticulture this bug is mainly found in bell pepper cultivation. In the first instance, in The Netherlands, the southern green stink bug was only spotted at the end of the summer, but the bug has also shown itself earlier in the season in recent years.

Females lay around 30 to 130 eggs at a time. They do this in "glued together", yellow and white clusters at the bottom of the leaf. If they are just laid, they look like little pearls. Depending on the temperature, the eggs hatch after 4 days to 3 weeks and the empty eggs remain on the leaf. The nymphs initially stay together and do not yet affect the plant. They then go through different stages, each time shedding their skin, with each stage having a different appearance. In the fifth stage, the bugs begin to spread over the plant and eat it.

Wednesday, 29 September 2021

Ficus carica petiole and Wacker 3A staining

Vascular bundles can be seen very well in these cross-sectional views of a leaf stem of the fig tree, thanks to the Wacker 3A triple staining. This coloring is done with a mixture containing Astra blue, Acriflavin and Acridine red.

We see the vascular bundles that lie in an outer circle, characteristic of (eu)dicotyledonous plants. In monocotyledonous plants, the bundles are irregularly distributed over the cross section. The Xylem vessels lie on the inward side and the Phloem vessels on the outside of the outer circle. Between Xylem and Phloem we see the intravascular Cambium. Vascular bundles are also present in the inner basic Parenchyma.

Due to the good uniform thickness of the coupe and the fine quality of the Moticam S12 camera, the photos could be taken without stacking.

Tuesday, 21 September 2021


Sundew or Drosera forms perfect rosettes to the ground and has red tentacles with a sticky, glittering droplet which is secreted by a gland. The flower owes its name to this. Small animals get stuck in the drop and are pushed by the moving tentacles to the leaf surface where they are digested.

Prepared slide by Lieder

Monday, 13 September 2021

Kahler's disease

The disease owes its name to the Austrian doctor Otto Kahler, who described the disease as one of the first. Kahler's disease, also called multiple myeloma, is a disease of the bone marrow caused by an uncontrolled proliferation of a certain type of white blood cells: plasma cells (also called plasmocytes). Plasma cells are responsible for the formation of antibodies under normal conditions.

The bone marrow is a spongy substance located in the interior of bones, especially the pelvis, sternum, ribs and vertebrae. Bone marrow plays a role in forming bones, but also in forming the cells of the blood: white blood cells (leucocytes), red blood cells (erythrocytes) and platelets (thrombocytes). The disease develops in one abnormal plasma cell, which divides uncontrollably and whose offspring also divides uncontrollably. Since they are all related, they only synthesize one specific type of antibody (or part of it). Since antibodies are proteins, the antibody produced is referred to as the "M protein" (from Myeloma protein). The name paraprotein is also commonly used for the M protein. When a specific piece (called “light chain”) of a paraprotein is found in the urine (or blood serum), it is called the Bence-Jones protein.

Friday, 10 September 2021

It grows on tree trunks

Dilated scalewort or Frullania dilatata grows mainly as a pioneer on trees with a moderately nutrient-rich bark. The species is somewhat drought-tolerant and can be found on free-standing trees, except in forests. Especially in full sun, the plants have their characteristic rust brown color. This moss experienced a decline in the last century due to air pollution, but is now common in almost all parts of The Netherlands. It is an attractive species, which is not easily overlooked in inventories. As a result, the distribution picture does suggest a greater number of occurrences than is actually the case: regularly there is only a single find per square section of land of 1 x 1 km.