MAURIVET

Penicillin - discovery

In contrast to the sulfa drugs, which were deliberately developed from a series of industrial chemicals, the first antibiotic was discovered by accident.

Alexander Fleming, a Scottish physician and bacteriologist, almost tossed out some culture plates that had been contaminated by mold. Fortunately, he took a second look at the curious pattern of growth on the contaminated plates. Around the mold was a clear area where bacterial growth had been inhibited. Fleming was looking at a mold that could inhibit the growth of a bacterium. The mold was identified as Penicillium notatum and later renamed Penicillium chrysogenum. In 1928 Fleming named the mold's active inhibitor penicillin. Thus, penicillin is an antibiotic produced by a fungus. The enormous usefulness of penicillin was not apparent until the 1940s, when it was finally tested clinically and mass produced.

By: Doctor On 12:09 PM

Antonie van Leeuwenhoek

He was a Dutch merchant and amateur scientist. He was probably the first person to observe live micro-organisms under magnifying lenses. He made a series of drawings of what he called as 'animalcules' i.e. small animals. He observed these by looking through his single-lens microscope at rainwater, his own feces and scrapings from his teeth. He made the drawings shown below.

By: Doctor On 6:31 AM

Tongue - papillae

The tongue is also called as the lingua or glossa. It is a highly muscular organ used for lapping water, prehension (grasping) of food, manipulating the food within the mouth and swallowing. It also possesses receptors for taste, temperature and pain.

It is covered with stratified squamous epithelium. In the anterior part, it forms specialized structures known as papillae. Based on their function they are grouped as mechanic papillae and gustatory papillae. Mechanic papillae are cornified and aid in licking while protecting the deeper layers. The gustatory papillae are covered with taste buds. Mechanical papillae are more numerous than gustatory ones.

The skeletal muscle of the tongue runs in three different directions. This allows for a wide range of movements needed to properly manipulate foodstuffs. The types, numbers and distribution of papillae in the tongue vary greatly among species.

In domestic animals there are usually five different types of papillae.

1) Filiform papillae are highly keratinized and sharply pointed. They aid in mechanically

breaking up food material. They are numerous in ruminants and cats where they are used in

lapping milk. They are the smallest and most numerous of all papillae.

2) Fungiform papillae are smooth with a rounded surface. They help manipulate the food

but also have taste buds on their lateral surfaces.

3) Conical papillae are somewhat larger than fungiform papillae. They are used in manipulating

and breaking down ingested food. They can be distinguished from fungiform papillae by

their larger size and their tendency to project above other papillae. They do not have taste buds.

4) Foliate papillae are covered with non-keratinized stratified squamous epithelium. They are leaf-shaped

structures defined by an invagination of the mucous membrane on their sides. Many

taste buds on their lateral surfaces indicate their role in gustation. They are absent in

ruminants but well developed in the horse and dog.

5) Circumvallate papillae are the largest (up to 1/8 inch diameter) papillae. They are

surrounded by a deep indentation of the mucous membrane and are not numerous. They do

not rise above the surface of the tongue. Many taste buds are located on their sides. Serous

von Ebner's glands empty into the "moat" around these papillae and help keep it free of food

particles.

By: Doctor On 3:51 AM

Erythropoiesis in animals

Erythropoiesis refers to the formation of red blood cells. It is a continuous process. Many nutrients are required for this notably, Vit B12, folic acid, amino acids and iron.

Vit B12 deficiency in humans cause macrocytic hypochromic anemia but in animals, though there is anemia the size of the RBCs are not much altered. Also cobalt is necessary in ruminants as they synthesize vit B12 in the rumen.

The stimulus for erythropoiesis appears to be the tissue need for oxygen. A reduced concentration of oxygen at tissue level results in the secretion of erythropoietin (EPO). The kidney is the major site (only site in dogs) for EPO production in adult mammals. It is produced by peritubular interstitial cells located within the inner cortex and outer medulla of the kidney. Liver is a minor extra-renal source of EPO in adults while in fetus it is a major site. In case of chronic renal failure in dogs, anemia is a common sequela as they cannot produce EPO elsewhere.

In bone marrow, EPO stimulates committed stem cells to increase their mitotic activity for a more rapid production and release of reticulocytes and mature erythrocytes into the circulation. EPO has a life span of less than one day.

By: Doctor On 3:58 AM

Life span of erythrocytes in animals

The life span varies with species.
In dogs, it varies between 100-130 days with an average being 118 days.
In cats, it varies between 70 and 80 days.
In horses, it varies between 140 and 150 days.
In adult ruminants (cattle,sheep and goats), it varies from 125 to 150 days while in lambs and calves, life span is shorter, ranging from 50 to 100 days.
Life span of erythrocytes in swine approaches that in human i.e. 100 to 120 days.

If the life span of erythrocytes is less than 100 days, then reticulocytes (immature erythrocytes) will be present in the blood of the animals in health. For animals like cattles and horses, there is no reticulocytes in their blood in health. Presence of reticulocytes implies anemia.

Erythrocytes from one animal infused into another animal of the same species do not live as long.

Birds have a shorter life span for erythrocytes may be due to their high body temperature and rapid metabolic rate. In chicken it is 20-30 days while for the duck it is 30-40 days.

By: Doctor On 3:29 AM