Distribution Of Mitotic Figures Research Articles

Frequent Mitotic Activity in Banal Melanocytic Nevi Uncovered by Immunohistochemical Analysis

The presence and distribution of mitotic figures is an important discriminatory parameter in the assessment of melanocytic lesions. We evaluated the number and distribution of mitotic figures in 353 randomly collected melanocytic nevi of various subtypes by hematoxylin and eosin (H&E) staining and immunohistochemically with the 2 mitotic markers Phospho-Histone H3 Ser28 (PHH3) and MPM2. At least 1 mitotic figure was present in 19.5%, 31.3%, and 42.8% of H&E-, PHH3-, and MPM2-stained lesions, respectively. In common compound nevi, the mean number of dermal mitoses amounted to 0.024/mm dermal surface area in the H&E staining (PHH3: 0.061; MPM2: 0.087) and to 0.175/mm in Spitz nevi (PHH3: 0.325; MPM2: 0.45). Nevi exhibiting mitotic figures were significantly more frequent in the youngest age group (0-20 years) than in patients older than 50 years (P < 0.0001). In the upper half of the dermis, mitotic activity was roughly 3 times as frequent as compared with the lower half. Clusters of mitotic figures within the dermis were not observed. Mitotic activity in obviously benign melanocytic nevi is not rare even in the deep dermal part. More than 2 mitotic figures per lesion can usually be explained either by the nevus subtype, young patient age, traumatization, or inflammation. PHH3 and MPM2 are a valuable diagnostic adjunct in the evaluation of melanocytic tumors allowing more sensitive and faster recognition of mitotic figures and their distribution.

Increase of mitotic activity in the colonic mucosa of patients with colorectal cancer.

A histologic and histochemical study of the colonic mucosa, including a study of the mitotic index, was performed in routinely processed specimens from control and tumor-bearing patients. A significant increase in the mitotic index (number of mitosis X 1000 gland cells), without concomitant modifications in the distribution of mitotic figures along the crypt depth, in mucosal thickness, or in mucin secretion, was demonstrated in the colonic mucosa of patients with colonic or rectal cancer compared with controls. The results point to an accelerated cell renewal in the colonic mucosa of tumor-bearing patients compared with the controls, without concomitant dysplasia. Results are discussed in the light of the possibility that an increased cell proliferation may have preceded the onset of tumor and played a role in the second step of carcinogenesis, i.e., tumor promotion, independently of dysplasia.

Decidual changes in the endometrium and morphological adaptation of the associated supplying arteries in the normal and diabetic pseudopregnant rat

After an electrically induced pseudopregnancy in rats in which deciduomas were produced by an intraluminal oil injection, the decidual tissue was studied morphologically on days 7, 10 and 13. A constant and dynamic wave of mitotic figures was found, which started on day 7 in the antimesometrial decidua, moving to the mesometrial decidua on day 10 and finally to the mesometrial triangle area on day 13 of pseudopregnancy. This and other morphological changes were compared with those found in pseudopregnant rats with streptozotocin-induced diabetes. On days 7 and 10 the incidence and distribution of mitotic figures were practically identical in both groups and statistically no significant difference was found in the uterine weight between the two groups on these two days. On day 13, two statistically significant differences were observed in the diabetic group: a fall in the uterine weight and a fall in the incidence of mitotic figures in the mesometrial triangle decidual cells. Associated with decidualization, a series of histological changes were studied in the arteries of the mesometrial triangle. Although the difference was not statistically significant, changes seemed to occur to a lesser degree in the diabetic group. It is concluded that the diabetic state has no influence in the early decidualization period, but it does have influence late in pseudopregnancy: a fall in the mitotic activity in the decidual tissue, a fall in the uterine weight and a less marked change in the spiral arteries which during pregnancy would supply the developing placenta with maternal blood.

Arrested growth of Chinese hamster ovary (CHO) cell colonies on agar.

Chinese hamster ovary (CHO) cells plated on agar form two classes of colonies; those which increase continuously in diameter and those which become arrested in outward growth. All colonies continue to increase in mass and thickness as demonstrated by computer-assisted analysis of time sequence photographs of several thousand colonies and by examination of histological sections. Colonies which shift from a monolayer to a mounded morphology at fairly large colony diameter (greater than or approximately 1 mm) continue to increase in diameter. Colonies in which mounding occurs at smaller colony diameter (less than or approximately 1 mm) cease to increase in diameter but continue to increase in thickness, as demonstrated by histological examination and by computer-assisted analysis. Rapid cell division occurs at the edge of all colony classes, as shown by the distribution of mitotic figures. In arrested colonies these dividing cells must move toward the colony core to compensate for dying cells. Necrotic cells are found as a discrete zone at the air-colony interface in all cases for CHO cell colonies growing on agar. As such, necrosis is probably due to limitations in nutrient diffusion upward from the agar rather than oxygen diffusion downward.

Peculiar pattern of interkinetic nuclear migration in the newt Notophtalmus viridescens.

The distribution of mitotic figures was studied in the neuroepithelium of Notophtalmus viridescens embryos of stages 14, 16 and 18. On the average, 34% of the mitotic figures were counted near the neurocoele (here in described as zone 1), 10% were recorded in the outer portion of the epithelium (zone 3) and 56% were found between these two regions (zone 2). It is concluded that this neuroepithelium is the site of interkinetic nuclear migration although its pattern is peculiar when compared to what occurs in the chick embryo. Also, the analysis of one micron-thick serial sections showed that the neuroepithelium in Notophtalmus viridescens is pseudo-stratified throughout neurulation.

The frequency and distribution of mitotic figures in dysplasia and carcinoma in situ.

The frequency and topographical (i.e. vertical and lateral) distribution of mitotic figures in normal cervical epithelium as well as in various degrees of dysplasia and in carcinoma in situ, was studied in punch biopsies and in subsequent cone specimens from 40 patients. The frequency of cells in mitosis in the whole thickness of the epithelium increased step-wise from normal epithelium to slight-moderate dysplasia, severe dysplasia and carcinoma in situ. A difference in the frequency of mitotic figures between slight and moderate dysplasia was recorded in the superficial cell layers of the epithelium. These findings, together with earlier reported differences in the frequency of DNA synthetizing cells between the various epithelial alterations support the validity of the histological classification of cervical atypias. Areas with mitosis alternated with areas without mitosis, supporting even here previous autoradiographical findings. The possible co-existence of proliferative and non-proliferative epithelial compartments in dysplasia and in carcinoma in situ of the uterine cervix is suggested.

Mitosis in the intact and regenerating planarian Dugesia mediterranea n.sp. I. Mitotic studies during growth, feeding and starvation

AbstractPlanarian neoblasts, the only cell type in this organism endowed with mitotic power, decrease in density as total body volume, total cell number, and length increase. Studies on mitosis show that the neoblast mitotic rate is a function of body length, being lower as the organism increases in length. The cephalo‐caudal distribution of mitotic figures in animals of different sizes shows a change towards a more even distribution of mitosis jointly with a mitotic increase in the caudal regions as length increases. However, in the sagittal and dorso‐ventral axes, the distribution of mitosis is always nonuniform, probably due to the uneven distribution of parenchymal tissue along them.The pharynx of animals in all size groups examined shows no mitotic figures except some near its base. This may suggest for this organ a proximal type of growth with some cell migration.Feeding elicits a very rapid increase in mitosis which lasts for almost a week, whereas long periods of starvation do not cause a significant increase or decrease in the basal mitotic rate. All these results stress the need of looking at the planarian neoblast mainly as a stem or replacement cell of most differentiated cell types and not as a mere “regeneration cell.” The implications of the results obtained for the mechanisms of growth and shrinkage are discussed.

Mycobacteria and Lymphoreticular Tumours in &lt;i&gt;Xenopus laevis, &lt;/i&gt;the South African Clawed Toad

Lymphoreticular tumours, mycobacterial granulomata and responses to antigens in Xenopus toadlets were compared. Lymphoreticular tumours and granulomata differed in histology, development, distribution of mitotic figures, involvement of small lymphocytes, aetiology and transmissibility. Combination experiments provided no evidence that Mycobacterium marinum plays a role in lymphoreticular tumour initiation and development, though, as in some human neoplasms, secondary mycobacterial infection was a feature of advanced tumours.

Studies on induced changes in growth patterns and polarity in roots of Vicia faba L.

Roots of Vicia faba were treated with colchicine (0.025%), or IAA (4.7×10(-6) M), or both, for 3 hours and fixed at various intervals over the following 11 days. The axis of spindle orientation and the distribution of mitotic figures, lateral root primordia and xylem vessel elements was examined in the apical 10 mm of median longitudinal sections of these roots.No effect of IAA was found on the orientation of the spindle. However, evidence was obtained indicating that the systems controlling the polarity of cell division and cell expansion differ in some way.The number of lateral root primordia formed was greater in roots treated with IAA or colchicine than in control roots. These primordia were always initiated adjacent to a xylem vessel. Thus, no primordium was closer to the apex than the most apical xylem vessel, suggesting that an endogenous factor involved in primordia initiation is transported in the xylem. The primordia which develop after colchicine treatment grow out as lateral roots; this is in contrast with those which form after IAA treatment and which do not undergo elongation. These results, which it must be emphasized apply only to the apical 1 cm of treated roots, indicate that lateral root primordia become sensitive to IAA at a certain stage in their development. Exogenous IAA acts as an inhibitor.The new meristem, which forms in the primary root apex after colchicine treatment, contains both diploid and polyploid cells, i.e. it was formed from cells that were unaffected and from cells that were affected by colchicine. Following colchicine treatment the size of the meristem shrinks and this can be prevented by treatment with IAA. This and other evidence presented here, suggests that IAA is a factor involved in the control of the size of the apical meristem in normal roots.

Distribution of Mitotic Figures in Different Regions of Lymph Node

Distribution of Mitotic Figures in Different Regions of Lymph Node

Mitosis During the Healing of X-ray Burns

CELLS lost by the epidermis after x-ray injury might conceivably be replaced through several processes. Mitosis of the remaining cells of the burned region is a method commonly described. Other possible means that have been described are amitosis (Kindred, 1927), lateral migration from nearby uninjured skin (Arey, 1932), modified mitosis (Stough, 1931), and migration and differentiation of cells of the dermis or of deeper layers of the body (Papanicoulaou, 1933, and Cameron, 1936). In the present series of experiments square burns 6 × 6 mm. were made on the backs of frogs by the application of 1,000 r. X-ray exposures were made in the laboratory of Professor L. J. Stadler, of the University of Missouri, with a Victor machine (Snook model), having mechanical cross-arm rectifier and universal type Coolidge tube operated at 140 kv.p. Tube current was 4 ma.; target distance, 11 inches; time, 7 minutes, 24 seconds. No screen or filter was employed. Each frog was chloretonized during exposure, and the size and location of the injury were regulated by the size and position of a square hole in the lead plate that shielded its body. The output of 136.5 r per minute was measured with a Victoreen dosimeter. Each week for 10 weeks following irradiation a frog was killed and a square of skin 18 × 18 mm. which had the burned square as its center was fixed in Bouin's fluid. A control square was taken from each frog. Each piece of tissue was cut into serial sections 6 mμ thick and stained with Mayer's hæmalum and orange G. In the distribution of mitotic figures and “travelling cells,” no differences were found between specimens cut along the longitudinal and those cut along the transverse axes of the animals. A certain amount of shrinkage in the burned area resulted in some distortion of the cells around the periphery of the burn and in the drawing of neighboring cells out of the perpendicular in the direction of the center of the burn, but no evidence of lateral migration was found. The very low percentage of cells in mitosis detected in rapidly growing tadpoles made the modified mitosis described by Stough a very attractive explanation of the source of the new cells. Nevertheless, nothing indicating modified mitosis was seen in the slides; only normal mitoses were found, which suggests that the cells in mitosis were not present in the epidermis at the time of exposure to x-rays but have subsequently arrived from the deeper layers of the body. One week after exposure the skin was reduced from six to five layers of cells; the control had three layers in the basal region in which metabolism was active but the irradiate had only two such layers. Many of the nuclei were swollen as though by excess fluid. The external layer of flattened cells was only loosely attached in the irradiate.