- SUBJECT: Mammalian red blood cells
- DATE: 3/97
-
- Does anyone know of any mammals with nucleated red blood cells? And
do
- you have a reference? Thanks for any help!
-
- ***************************************************************
- Louise Baxter email: baxterl@cwu.edu
- Department of Biological Sciences phone: 509-963-2745
- Central Washington University fax: 509-963-2730
- Ellensburg, WA 98926
-
-
- Blood lesson time.
- 1. Vertebrates have oval, nucleated, hemoglobin containing red cells:
- there is an exception, mammals - where the cells are round, biconcave,
- and anucleate in the circulating peripheral blood. And there is an
- exception within the mammals: camel circulating red cells are oval,
not
- round; they are however, anucleate.
- 2. All vertebrate red cells, including mammalian are nucleated at one
- time. The normoblast of mammalian red cells lose their nucleus before
- the cell is released into the peripheral blood. Sometimes the remodeling
- of the mammalian red cell is incomplete at release time and traces
of ER
- etc are still present; these cells are called reticulocytes. Within
a
- day or two in the circulating blood, the red cell has its usual appearance.
- 3. Now for some possible confusion. Vertebrates except mammals have
- thrombocytes, a small nucleated cell involved in clotting. Mammals
have
- anucleated fragments (notice a trend) called platelets.
- 4. Blood trivia: a human red blood cell has a surface area of about
140
- microns2. One third of the cell's mass is hemoglobin of which there
are
- about 265,000,000 molecules per cell. The total surface area of all
the
- 25 trillion human circulating red cells is about 4,000 m2. A red cell
- will make about 50,000 circuits through the body before it is removed
- after about 120 days.
-
- A question I pose to my students. If the characteristic shape of a
- vertebrate red cell is oval and nucleate, then one would assume that
- blood capillaries evolved in such a way as to take advantage of the
shape
- of the red cell. Because mammalian red cells are round, biconcave and
- anucleate, are the capillaries designed differently to accommodate
- possible differences in fluid dynamics?
-
- Some final comments: Several biological supply houses sell camel blood
- because of it shape difference. And dalmations have different hemoglobin
- from the rest of the "usual" mammals.
-
- Ain't Spring Break grand!!
-
- Blystone in Texas
-
- --------------------------------
- Robert V. Blystone, Ph.D.
- rblyston@trinity.edu
-
- Department of Biology
- Trinity University
- 715 Stadium Drive
- San Antonio, Texas 78212
- 210.736-7243 FAX 210/736-7229
-
-
- Blystone in Texas included the following (in celebration of
- Spring Break!!):
- ******************************************************************
- 3. Now for some possible confusion. Vertebrates except mammals have
- thrombocytes, a small nucleated cell involved in clotting. Mammals
have
- anucleated fragments (notice a trend) called platelets.
- *****************************************************************
- Robert:
- Can you provide your reference for the above? I just checked, in haste,
- two current human anatomy/physiology texts and they both indicated
that
- thrombocytes = platelets; i.e., thromobocytes are "fragments"
of cytoplasm
- surrounded by a membrane and without a nucleus. Is this the situation
- of human anatomists/physiologists NOT recognizing that mammals are
different
- from other vertebrates?
- Jim Freed in Ohio.
-
-
- >Is this the situation
- >of human anatomists/physiologists NOT recognizing that mammals
are different
- >from other vertebrates?
-
- Bloom and Fawcett A Textbook of Histology 10th edition page 140. "The
- blood of reptiles, birds, amphibians, and lower vertebrates does not
- contain platelets but has nucleated cells called thrombocytes, which
seem
- to play a similar role in blood clotting."
-
- I guess Don Fawcett has it right.
-
- Blystone in Texas
-
- --------------------------------
- Robert V. Blystone, Ph.D.
- rblyston@trinity.edu
-
- Department of Biology
- Trinity University
- 715 Stadium Drive
- San Antonio, Texas 78212
- 210.736-7243 FAX 210/736-7229
-
-
- I believe it is definite that no mammals have nucleated red blood cells.
Check any
- recent zoology text. Some of these texts used to report that Camelids
and Prototherians had red blood cells, but they were simply repeating an
erroneous claim from another text. When someone looked, the claim was wrong.
-
- Dave McNeely, Biology, University of Texas at Brownsville, 80 Fort
Brown, Brownsville, TX 78520; mcneely@utb1.utb.edu
-
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