Nuclei Information and Courses from MediaLab, Inc.

Seven mesothelial cells are seen in this slide. Notice that all of the nuclei have a distinct shape with no evidence of irregular division. Chromatin pattern is typical of cells that originate in the tissues. Cytoplasm is irregular and some pseudopods are evident, especially in the lower portion of the field.

Four blast cells are seen in this field. Notice the smooth chromatin pattern, nucleoli, high NC ratio and irregularly shaped nuclei. These blasts were observed in a spinal fluid sample from a patient with acute lymphocytic leukemia.

Many lymphocytes are present in this field. Two larger, atypical lymphocytes with intact cytoplasm and slightly indented nuclei are seen near the center of this slide. Two other large cells with irregular, trailing cytoplasm are macrophages (histiocytes). Increased lymphocytes may be seen in viral meningoencephalitis, partially treated bacterial meningitis, multiple sclerosis, Guillian-Barre's syndrome, or polyneuritis.

Within the hematopoietic cords each cell line has a specific location for development. Erythroid precursors are located near a venous sinusoid and cluster around a macrophage. This is referred to as an erythroblastic island. Developing red cells obtain iron needed for hemoglobin production from macrophages. Megakaryocytes are also located close to a venous sinus. They extend their cytoplasm in fingerlike projections through the sinus wall in order to release their platelets directly into the blood in the sinus. Immature granulocytes lie within the hematopoietic cords. The metamyelocyte stage is the first stage of the granulocyte series that is motile and able to move toward the sinus area. Mature neutrophils, eosinophils and basophils enter the sinusoidal blood through the basement membrane. As maturing erythrocytes also move toward the sinus wall any remaining nuclei are lost as the red cells move through small openings in the cells lining the sinus wall.

It is also important to scan the slide for the presence of other large cells which are not usually seen in normal marrow. An osteoclast is an example of this type of cell. Osteoclasts are large multiinucleated cells (up to 100 microns) which may be confused with megakaryocytes. One striking difference is that an osteoclast has multiple nuclei which are separate from each other. The multiple nuclei in the megakaryocyte are joined together. The cytoplasm, although somewhat finer in texture, could be mistaken for platelets.

Lymphocytes "transform" in response to antigenic stimuli.Their nuclei becomes larger with more open chromatin and a greater degree of nuclear folding.The cytoplasm becomes abundant, the number of azurophilic granules may be increased and vacuoles may be present.The cytoplasmic membrane may be easily indented by surrounding red blood cells, resulting in a scalloped appearance of the cell's outer edge.These lymphocytes may also be referred to as reactive, activated or stimulated.

The granulocytes found in normal peripheral blood are neutrophils, eosinophils and basophils.Most have segmented nuclei, and are therefore classified as being at the "segmented" stage of development. Some that are a little less mature have unsegmented nuclei. These are classified as "bands." Generally, we differentiate between the band and segmented forms of neutrophils, but since eosinophils and basophils are present in such low numbers, and since their nuclei are often obscured by cytoplasmic granules, we usually don't concern ourselves with designating the band forms.Since hematologists and textbooks use several different terms for these cells, synonyms for each term will be given and then may be used interchangeably throughout the course.

The nucleus of the large lymphocyte is larger than that of the small lymphocyte, and is more irregular in shape. Sometimes it is rounded, oval or indented.

Monocytes have generally lighter staining nuclei than do other leukocytes. The nucleus stains a pale bluish-violet, and the chromatin is fine and skein-like.

The Sternheimer-Malbin (SM) stain is a commonly used supravital stain containing crystal-violet and safranin. WBC's, epithelial cells, and casts stain well with SM stain. Sedi-Strain (Clay Adams, Sparks, MD) and Kova stain (ICL Scientific) are among those commercially available. Nuclei and cytoplasm of various cells can be stained with a 0.5% solution of toludine blue.

The natural history of TB infection is usually followed by an immune response and latency after exposure. In about 5-10% of cases, the latent period progresses to an active infection.The organism that causes TB infection is Mycobacterium tuberculosis. This organism is pictured in the photograph to the right as observed when stained with acridine orange stain. Infection occurs when a susceptible person inhales droplet nuclei containing Mycobacterium tuberculosis and the organism reaches the alveoli of the lungs.About 2-12 weeks after infection, the immune system limits multiplication of additional bacteria and the immunological test becomes positive.Latent tuberculosis infection (LTBI) is the stage when the viable organism remains in the body, and the patient has no symptoms and is non-infectious.Most infected persons do not experience clinical illness and are noninfectious. About 5-10% of persons infected with Mycobacterium tuberculosis who are not treated will develop TB during their lifetime. The risk for progression is highest during the first several years after infection.TB infects the lungs most often; however, it can infect almost any organ in the body, including bones and joints.

A normal bone marrow smear stained with Wright/Giemsa stain is captured in this photograph.Note the normal maturation sequence beginning with myelocytes (the two large cells in the left upper corner)through metamyelocytes, band neutrophils,and multi-lobed segmented neutrophils.The small cells with darkly staining, centrally placed nuclei are normoblasts (three are clustered in the left lower field).Absent in this field are eosinophils, basophils and megakaryocytes.A normal M:E ratio of 2.4:1 is calculated from the twelve myeloid cells and five normoblasts. Two lymphocytes are identified, one left center, the other left upper.

The Pelger-Huet anomaly is a congenitally acquired condition of nuclear segmentation and is clinically insignificant. There is no loss of cellular function.The condition can be suspected if typical bilobed, "pince-nez" nuclei are observed (left upper frame in the composite photograph).Band neutrophils usually have two distinct lobes, connected by a relatively short but thick bridge as illustrated in the upper and lower right frames. Monolobated cells may also be encountered, as illustrated in the lower left frame. If these are seen in significant numbers, the possibility of a homozygous Pelger-Huet should be considered.