Abnormal Mitotic Figures Research Articles

Genital warts and cervical cancer: VI. The relationship between aneuploid and polyploid cervical lesions

Human papillomaviral infection is now widely implicated in the causation of cervical neoplasia. Genotype analysis provides the best guide to biologic outcome; most polyploid lesions regress and most aneuploid ones persist or progress. This prospective survey examined the relationships between cell ploidy and 24 objectively validated criteria of human papillomaviral infection or premalignant change in 52 biopsies from a dysplasia clinic. Histologic evidence of benign warty expression and human papillomaviral capsid antigen production decreased steadily as DNA content ranged from diploidy to polyploidy to aneuploidy. In contrast, premalignant change increased with progressive distortion of nuclear DNA content. No absolute discriminants were found between polyploidy and aneuploidy, as evidenced by the detection of human papillomaviral proteins in three of 21 aneuploid epithelia and the recognition of abnormal mitotic figures in five of 17 polyploid lesions. Polyploid and aneuploid lesions differed only in severity, and it appears that some polyploid epithelia may be transition forms between diploidy and aneuploidy.

Human Papillomavirus Type 16 and Early Cervical Neoplasia

Flat warts (condylomata) of the uterine cervix are sometimes cytologically atypical and have abnormal mitotic figures; they are thought to be possible precursors of cancer of the cervix. Flat warts are caused by any of a number of types of human papillomaviruses (HPVs), one of which (HPV 16) has been previously associated with invasive cancer of the cervix. To determine whether HPV 16 is also associated with flat warts with abnormal mitoses, we analyzed 23 flat warts by DNA-hybridization techniques for the presence of HPV 16 and other HPV types, and correlated the results with the histology. Of 10 lesions with abnormal mitotic figures, 7 contained HPV 16, and 1 contained another type of HPV. Of 13 lesions without abnormal mitotic figures, only 1 contained HPV 16, and 7 contained other types of HPV. We conclude that the presence of HPV 16 correlates with the presence of abnormal mitotic figures in flat warts of the cervix, and that this type of flat wart is a precursor of invasive cancer of the cervix.

Koilocytotic lesions of the cervix. The relationship of mitotic abnormalities to the presence of papillomavirus antigens and nuclear DNA content.

It has been reported that abnormal mitotic figures (AMFs) occur principally in aneuploid lesions and that aneuploidy is a diagnostic feature of non-endocrine-dependent epithelial cancer precursors and cancers. Recently, AMFs have been reported in cervical lesions interpreted as flat condylomata, and it has been suggested by several authors that AMFs may not be diagnostic or aneuploidy or neoplasia, particularly in human papillomavirus-(HPV)-induced lesions. Although it is conceivable that AMFs may be a regular feature of HPV infection, their association with cytologic atypia and their presence in higher grades of cervical intraepithelial neoplasia (CIN) suggests that AMFs may herald the presence of a different lesion than the pure flat condyloma. In the current study, koilocytotic cervical lesions thought to be HPV-induced were examined microscopically for the presence of AMFs, and the findings were correlated with the presence of HPV as determined by immunoperoxidase and nuclear DNA distribution patterns as measured by Feulgen microspectrophotometry. In unselected lesions originally diagnosed as flat cervical condylomata, AMFs were surprisingly common (22.6%), and did not correlate with the extent of koilocytosis. Immunoperoxidase (IMPO) stains were performed in 35 cases with AMFs, and were negative for HPV in 74.3% and positive in 22.8%. However, among the cases evaluated by IMPO, there was an inverse relationship between the presence of mitotic abnormalities and the expression of HPV antigen. Nine of 11 (81.8%) lesions containing AMFs were aneuploid, and 2 of 11 (18.2%) were polyploid. Abnormal mitotic figures have a range of morphology and frequency in koilocytotic cervical lesions. Although the biology of these lesions is not well-defined, the presence of AMFs may identify a subgroup of HPV-induced cervical atypias which represent a transition between flat cervical conylomata and CIN.

Correction

In the June 10 MEDICAL NEWS story on the link between human papilloma virus and cancer (1983; 249:2998), one photo caption should have read, "Abnormal mitotic figures in cervical intraepithelial neoplasia...."

Meiosis and early cleavage in Drosophila melanogaster eggs: effects of the claret-non-disjunctional mutation.

The claret-non-disjunctional (cand) mutation is a female-specific mutation in Drosophila melanogaster, which causes a high frequency of mortality (89--90%) in eggs laid by the homozygous females. Among the progeny that survive to the adult stage, greater than 50% are aneuploid and/or mosaic for the X and number 4 chromosomes. The genetic studies of cand indicate that it is homologous to the claret mutation (ca-simulans) in Drosophila simulans. The cytological effect of the cand mutation on meiosis I and the early cleavage divisions has been observed at the light microscope level in stage 14 ovarian and fertilized uterine eggs, respectively. Four classes of metaphase I figures were observed. These include those with: (1) two or more spindles; (2) spindles that were abnormally wide and the bivalents widely separated; (3) unipolar spindles; and (4) apparently normal bipolar spindles. The three abnormal classes of metaphase I figures included 80% of the eggs examined at this stage. Among the cleavage stage eggs examined 69% showed highly abnormal mitotic figures, including multipolar spindles, and the nuclei in these eggs were found in clusters, rather than dispersed throughout the ooplasm. In addition to the cytological abnormalities observed, 17--23% of the eggs produced by the cand females showed morphological abnormalities. These abnormalities included eggs having three of four dorsal filaments, eggs that had a truncated shape, and abnormally small eggs. These abnormalities may not be an aspect of the cand syndrome, but they are due to recessive genes located on the third chromosome. Although the cand and ca-simulans mutations both affect the formation of the spindle apparatus during meiosis and the early cleavage divisions, the effects of these two mutations differ considerably in detail. The effect of the ca-simulans mutation appears to be more severe than the effect of cand. A model to explain the relationship between the effect of the cand mutation on meiosis I and the early cleavage divisions is presented, and evidence to support the model is discussed.

Studies of mitosis in excised limb regenerates of the newt, Notophthalmus viridescens.

Subsequent to excision and explantation of the limb blastema into culture medium, there is an abrupt reduction in mitotic index lasting several hours. Coincident with the disappearance of mitosis, abnormal mitotic figures (AMFs), lacking the condensed chromosomal nature of normal figures, are seen. These persist until normal levels of mitotic activity are restored approximately 6 hr later. The transient loss of mitotic activity is observed in both ganglionated and nonganglionated explants. The large number of prophase figures observed at time zero were sharply reduced within minutes, without concomitant increases in the later phases. The possibility that some cells, without completing mitosis, become temporarily indistinguishable as mitotic figures, is discussed in terms of chromosomal decondensation and recondensation.

Morphological changes of myofibril in the carcinogenetic course of 20-methylcholanthrene-induced rhabdomyosarcoma.

In this study 20-methylcholanthrene (MC) was embedded in skeletal muscle tissue of mice. The resulting morphological changes were observed by light and electron microscope until the occurrence of rhabdomyosarcoma. The injected region of the muscle tissue in which MC was embedded went through three stages: destruction and degeneration, repair and appearance of atypical cells. The morphologic figures of the myofibrils seen in the skeletal muscle cell during destruction and degeneration were similar to nonspecific. The muscle tissue then regenerated in the same manner as seen during experimentally induced muscle tissue regeneration in both humans and animals. Abnormal mitotic figures were found 60 to 70 days after the injection of MC. Immature muscle cells, with tuft-formed myofibrils present, underwent abnormal mitosis in which one of the nuclei divided. The rhabdomyosarcoma cells produced by this abnormal mitosis began to appear in the lesion 70 days after the initial embedding of MC. The rhabdomyosarcoma cells in the induced tumor formed undifferentiated myofibrils in various degrees of maturation, and were therefore considered to play a part in the abnormal myofibrillar formation.

Relationship of in vitro morphologic and growth characteristics of established human glioma-derived cell lines to their tumorigenicity in athymic nude mice.

Fifteen permanent cell lines derived from human gliomas which are individually distinct by immunologic and biochemical criteria were evaluated to determine if morphologic or cell biologic parameters distinguished the 4 lines which were tumorigenic in athymic nude mice. By subjective morphologic appraisal, the 4 tumorigenic lines were considered "malignant" or "borderline," but 4 of the non-tumorigenic lines were also classified in this way. By objective criteria, these 15 lines varied markedly in percentage of piled-up cells, chromatin pattern, pleomorphism, nuclear to cytoplasmic ratio, number of bizarre multinucleate giant cells, presence of abnormal mitotic figures, percentage of colony formation in soft agar, saturation density, population doubling time, and absolute plating efficiency. Among these criteria, percentage of colony formation in soft agar had the highest correlation coefficiency with tumorigenicity, and when this parameter was held constant the only additional characteristic which correlated significantly (p less than .05) was the number of bizarre multinucleate giant cells. When the 11 non-tumorigenic lines were ranked by these 2 criteria, 1 non-tumorigenic line (U-251 MGsp) had greater than .95 predicted probability of tumorigenicity. Although further tumorigenicity testing may increase the number of tumorigenic lines, the lines with few "malignant" characteristics may correspond to the population resembling cells of low grade astrocytomas seen within glioblastomas. The histologic pleomorphism of human gliomas is reflected in their morphologic and cell biologic diversity in culture.

A correlative nuclear DNA and histologic study of genital squamous lesions in DES exposed progeny.

72 vaginal and cervical squamous lesions from 55 DES-exposed young women were analyzed using the technique of Feulgen microspectrophotometry to correlate the nuclear DNA content with histologic changes and follow-up data. A euploid pattern was observed in 23 specimens (14 cervical and 9 vaginal) histologically classified as immature squamous metaplasia. Of the 49 significant squamous abnormalities, 17 (9 cervical and 8 vaginal) were polyploid, and 32 (26 cervical, 5 vaginal, and 1 pericervical collar) were aneuploid. Most of the lesions with polyploid patterns were histologically classified as atypical metaplasia or slight dysplasia, while most of the aneuploid lesions were moderate and severe dysplasias. Conservative therapy usually eradicates polyploid lesions with no recurrence; in contrast, a high recurrence rate is seen in patients with aneuploid lesions managed with biopsy and/or therapy. The presence of abnormal mitotic figures in aneuploid lesions is the most significant histologic feature which differentiates aneuploids from polyploids. The biologic behavior of lesions can be better appreciated if histologic findings are supplemented with nuclear DNA data.

THE COMPARATIVE CELL CYCLE AND METABOLIC EFFECTS OF CHEMICAL TREATMENTS ON ROOT TIP MERISTEMS. I. IOXYNIL

In this study we investigated the cell cycle response of Vicia faba and Pisum sativum root tip meristems to ioxynil treatments at two concentrations, (10−‐4m and 10−‐6m). After 24 h of treatment at 10−‐4m concentration, O2 uptake and ATP concentrations were significantly reduced. The mitotic index was reduced and the cell cycle population position was shifted to indicate that previously inhibited cells reformed their nuclei and became tetraploid. Prolonged treatment at this concentration resulted in cell death. Treatment with ioxynil at 10−‐6m reduced the rate of entry into mitosis. Abnormal mitotic figures in all stages were observed, and the ploidy level of mitotically inhibited cells was doubled. These observations indicated that at 10−‐6m concentration ioxynil acts as a preprophase inhibitor, that is, it does not act directly on the mitotic apparatus but does affect processes on which mitosis depends.

The Comparative Cell Cycle and Metabolic Effects of Chemical Treatments on Root Tip Meristems. I. Ioxynil

In this study we investigated the cell cycle response of Vicia faba and Pisum sativum root tip meristems to ioxynil treatments at two concentrations, (10−-4m and 10−-6m). After 24 h of treatment at 10−-4m concentration, O2 uptake and ATP concentrations were significantly reduced. The mitotic index was reduced and the cell cycle population position was shifted to indicate that previously inhibited cells reformed their nuclei and became tetraploid. Prolonged treatment at this concentration resulted in cell death. Treatment with ioxynil at 10−-6m reduced the rate of entry into mitosis. Abnormal mitotic figures in all stages were observed, and the ploidy level of mitotically inhibited cells was doubled. These observations indicated that at 10−-6m concentration ioxynil acts as a preprophase inhibitor, that is, it does not act directly on the mitotic apparatus but does affect processes on which mitosis depends.

Cell Cycle Population Kinetics of Pea Root Tip Meristems Treated with Propham

Propham (Isopropyl carbanilate) at 10-5M concentration does not inhibit DNA synthesis nor does it reduce the number of dividing cells. It does, however, induce a number of abnormal mitotic figures. At higher concentrations (10-3M) propham inhibits DNA, RNA, and protein synthesis as well as stopping entry of cells into mitosis and causing those which divide to be aberrant. DNA and RNA synthesis are not inhibited for approximately 3 hr, while protein synthesis is reduced within 1 hr. The metabolic inhibitory effect of propham is reversible at least in roots treated for 8 hr. The most likely mode of action of propham is the inhibition of certain mitotic specific proteins, or possibly some kind of protein binding function as has been suggested in the literature.

Karyological instability of neoplastic somatic cells.

It is logical and conservative to theorize that the neoplastic process in mammalian cells is caused by alterations in the function of chromosomal chromatin (DNA), although there is a possibility that the malignant state is caused by epigenetic factor(s) within the cell residing outside the DNA and the nucleus. The role of chromosomal variability which may be present in many forms of neoplastic growth has been a challenge to cytogeneticists since the time of von Hanseman (1) in 1890 and Boveri (2) in 1914. They suggested that abnormalities of the mitotic process and of chromosome constitution were essential characteristics of the neoplastic cell. Boveri's theory, based on his studies of abnormal mitotic figures during development of the sea urchin embryo, was that malignant cells are mutant clones that acquire a genetically unbalanced complement (aneuploidy). This conclusion seems puzzling because there is no evidence that malignant tumors occur in echinoderms. However, Boveri's contentions were verified approximately 40 years later by Makino (3), who studied malignant cells of an azo dye induced Yoshida ascites tumor and determined that it contained one large metacentric chromosome. At about the same time, Hauschka and Levan (4) applied the squash technique to ascites cells in suspension. Serially passed tumor lines, both spontaneous and chemically induced, had chromosome modes that ranged from hypodiploid to hypertetraploid; no prominent marker chromosome was found, but it was evident that these tumors were characterized by a specific stemline (5). In primary tumors examined at the earliest possible stage of development, a normal chromosome complement could be present (5, 6). Examination of preneoplastic pulmonary adenomas of mice indicated that multiple tumors in the same animals could be either diploid, pseudodiploid, or aneuploid, although there was a predominance of aneuploid tumors (7). Thus, multiple tumors that arise independently may present chromosome complements that differ from one cell line or tumor line to the other. As

Effect of fluorodeoxyuridine, colcemid, and bromodeoxyuridine on developing neocortex of the mouse

AbstractThe purpose of this study was to obtain information about factors controlling the interkinetic movement of neuroepithelial cells and the cortical migration of neuroblasts in the developing mouse neocortex. In the first experiment 15‐day pregnant mice were injected with a single dose of fluorodeoxyuridine, a compound which inhibits the enzyme thymidylate synthetase thus blocking DNA‐replication. The animals were sacrificed at various hours and days following treatment. Two hours after treatment the mitotic index of the neuroepithelial cells was severely reduced and cells with abnormal nuclei appeared in the DNA‐synthesizing zone of the neuroepithelial layer. By five hours more abnormal cells appeared and many showed degenerating nuclei. By 12 hours cells with abnormal nuclei were seen in the outer half of the neuroepithelial layer and some in the migratory zone. Since they were not seen at the lumen, these observations indicate that fluorodeoxyuridine‐affected nuclei do not move to the lumen and do not divide. By 24 hours abnormal nuclei were seen in the migratory zone and cortical plate suggesting cortical migration without preceding cell division. In the second experiment 15‐day pregnant mice were treated with col‐cemid, a compound which arrests dividing cells in metaphase. Two and four hours after injection a large number of neuroepithelial cells in metaphase accumulated at the lumen. By seven and 12 hours the number of arrested metaphases decreased rapidly, but at the same time cells with dense, darkly stained nuclei appeared in the adjacent neuroepithelium. By 24 hours these abnormal nuclei were present in the migratory zone and cortical plate, suggesting that they were migrating towards the surface of the cortex despite the failure to complete mitosis. In the third experiment 15‐day pregnant mice were injected with bromodeoxyuridine, a compound incorporated into DNA and thought to interfere with differentiation. During the first 12 hours after treatment a striking increase in the number of normal mitotic figures was seen at the lumen. By 16 hours, however, abnormal mitotic figures started to appear. Since the generation time of neuroepithelial cells at this stage of development is about 13 hours, the abnormal mitotic figures must represent cells which have gone through two DNA‐synthetic periods since the beginning of the treatment. The abnormal mitotic figures give rise to cells with dense pycnotic nuclei which by 24 hours are found throughout the width of the developing neocortex. Thus in each experiment cells with abnormal, presumably non‐functional, nuclei were produced. Despite the failure to divide or to carry out a normal division, the nuclei migrate from the neuroepithelial layer towards the cortical plate in a fashion similar to that of normal postmitotic neuroblasts.

Cerebral cortex of the mouse after prenatal chemical insult.

AbstractThe purpose of this study was to examine whether a short term chemical insult to neuroepithelial cells (the matrix cells of neurons) causes a clearly defined neuronal deficit in the neocortex and hippocampal region. In the first experiment 15‐day pregnant mice were given a single dose of 5‐azacytidine (4 mg/kg); 30–60 minutes later they were injected with tritiated thymidine (6 μc/g). The fetuses were sacrificed at various hours and days after treatment. No cellular abnormalities were observed one or two hours after treatment with 5‐azacytidine, but at three to four hours abnormal mitotic figures became visible at the lumen. Usually the chromosomes were clumped together, forming commaand circle‐shaped structures. Sometimes chromosome breaks were observed. The number of cells with chromosomal abnormalities increased during the following hours, but ten hours after treatment a few normal mitotic figures appeared again. In the meantime the affected cells moved from the lumen toward the cortical plate. Their number gradually decreased and 48 hours after treatment all had disappeared. Since in the controls many labeled cells reached the cortex but in the experimental animals none, a neuronal deficit resulted from the treatment. It was difficult, however, to pinpoint the type of neuron lacking in the brain of the treated newborn. In the second experiment pregnant animals were given several doses of 5‐azacytidine (2 mg/kg on days 13, 14 and 15 of gestation) and sacrificed at various days after birth. The neocortex as well as the hippocampal region of the treated animals contained fewer cells than the same structures in the controls. In addition many neurons both in the cortex and hippocampus were morphologically abnormal. It is thus concluded that single and repeated shortterm chemical insults to neuroepithelial cells during the later stages of fetal life, result in a shortage of neurons and the presence of morphologically abnormal neurons.

Abnormal mitotic figures and giant cells in guinea-pig bone marrow exposed to rabbit anti-thymus serum or anti-bone marrow IgG.

DURING quantitative in vivo studies of the effects on guinea-pig bone marrow cells of rabbit anti-thymus serum and of rabbit anti-bone marrow IgG, abnormal mitotic figures, giant cell neutrophils and cells with karyomeres have been seen in bone marrow smears.

Proliferation kinetics of x-irradiated mouse L cells studied WITH TIME-lapse photography. II.

SummaryProliferation kinetics of x-irradiated mouse L-P59 fibroblasts were studied by constructing cell pedigrees from photographic records. Parameters of proliferation showed marked age dependence; early G1 cells were most resistant and late S-G2 cells were most sensitive in terms of reduction in probability of division, increase in generation time, and induction of abnormal mitotic figures (multipolar and incomplete mitoses). Division probabilities were higher at first division than at subsequent divisions, and cell death in some pedigrees was absent until the fourth generation or later. Prolongation in generation time occurred during several post-irradiation divisions, most noticeably in abortive clones. The idea that chromosome damage may not be the major cause of cell killing is suggested by the observations that (1) frequency of first division lethal sectoring showed no age dependence; (2) multipolar mitosis appeared to account for a significant proportion of non-surviving clones at low doses.

The retinal pigment epithelium. I. Comparative histology.

The comparative histology of the retinal pigment epithelium (RPE) of the following species was studied by examining bleached flat preparations and cross sections of the cells: human, monkey, rat, rabbit, sheep, cow, dog, and chicken. The variations noted among the cells of the different species involved cell size, nuclear size, number of nuclei per cell, and the distribution of pigment granules within the cells. The majority of the retinal pigment epithelial cells of the rat and rabbit were binucleate; binucleate RPE cells were common in primate eyes and were noted occasionally in other species. Normal and abnormal mitotic figures were observed in the retinal pigment epithelium of two apparently normal adult albino rats.

Liver response tests. VI. Application to a comparative study of food antioxidants and hepatotoxic agents

The toxicological significance of hepatomegaly induced by chemical agents has been studied by comparing the response of the liver after exposure of rats to one of 3 hepatotoxins, or one of 3 food antioxidants, followed by a period of recovery. Changes in the following liver parameters were investigated: relative weight; activities of certain enzymes, assessed biochemically and histochemically; histological picture. The hepatotoxins were administered by stomach tube daily for 1 wk at 2 dose levels (mg/kg) as follows: carbon tetrachloride (160, 1600; single doses only); ethionine (10, 100) and coumarin (20, 200). The antioxidants, butylated hydroxytoluene (BHT; 3,5-di- tert-butyl-4-hydroxytoluene), butylated hydroxyanisole (BHA; 3- tert-butyl-4-hydroxyanisole) and propyl gallate (PG) were similarly administered at graded dose levels ranging from 50–500 mg/kg. Liver enlargement was only conspicuous with coumarin, BHT and BHA. Carbon tetrachloride, coumarin and ethionine brought about a decrease in glucose 6-phosphatase with a simultaneous increase in glucose 6-phosphate dehydrogenase activity. BHT affected both enzymes, but only at a dose of 500/mg/kg, whereas BHA and PG did not alter the activity of either enzyme. Substantially the same conclusions were drawn from histochemical studies, which also revealed that the loss of glucose 6-phosphatase activity was predominantly perilobular. The histological alterations in the liver consisted mainly of fatty change, most striking in the case of carbon tetrachloride, less so with ethionine and PG, very slight with coumarin and BHT, but not seen with BHA. There was an unexpected incidence of abnormal mitotic figures in the group treated with PG which were still present after 14 days' recovery but had completely disappeared by day 28. After recovery, a clear distinction could be drawn between the ready reversibility of the liver response to the food antioxidants, compared with the greater persistence of the effects on the liver induced by hepatotoxins; for example, after 14 days the depressed activity of glucose 6-phosphatase was still manifest, only returning to the normal level by day 28. Fatty change induced by carbon tetrachloride and coumarin persisted, though at a reduced level, throughout the 28-day recovery period in contrast to the rapid disappearance of this effect elicited by BHT and PG. Further evidence to show that, as a rule, hepatotoxic agents do not stimulate processing enzyme activity has been provided by a study demonstrating the lack of effect of 7 daily doses of 200 mg coumarin/kg on hexobarbitone oxidase, nitroanisole demethylase and aminopyrine demethylase in the liver of rats.

CYTOTOXIC EFFECTS OF THE MYCOTOXINS OF PENICILLIUM ISLANDICUM SOPP, LUTEOSKYRIN AND CHLORINE-CONTAINING PEPTIDE ON CHANG'S LIVER CELLS AND HELA CELLS.

Summary The cytotoxic effects of mycotoxins of Penicillium islandicum Sopp, luteoskyrin and chlorine‐containing peptide, were examined in tissue culture cells. For both CL cells and HL cells, Lt. inhibited the cell growth at concentrations higher than 0.12 μg/ml and affected the cells lethally at the concentration of 1.2 /μg/ml. Pt. inhibited the growth of CL cells at 3.17 /μg/ml and that of HL cells at 10/ng/ml, showing a slightly different susceptibility with each other. With Pt. at higher than 31.7/ig/ml, both cells were affected lethally. The cytological changes induced by Lt. were characterized by the cell atrophy in spindle shape, appearance of large fat granules in the cytoplasm, atrophic nuclei with unevenly distributed chromatin substances, rounded nucleoli, multinucleosis, and slight swelling of the mitochondria and endoplasmic reticulum. These changes were marked above the concentration of 0.34 μg/ml after 2 days.The most characteristic changes caused by Pt. was vacuolation and hyaline‐dropletlike degeneration. Other changes were abnormal mitotic figures, irregularity in cell size, needle‐like substances in the cytoplasm, multinucleosis and electron‐microscopical fine granular matrix, cystic distension of the mitochondria and disappearance of the microvilli. These changes appeared at the concentration of 10/μ/ml within a day.These changes are closely correlated to the findings in the liver parenchymal cells in vivo affected with respective toxins. Cells growing in the toxin‐free media after the intermittent toxin treatments showed cellular pleomorphism with Lt. and appearance of somewhat larger cells with Pt., both of which exhibited an increase in the resistance to respective toxins. The animal LD5o and the concentration affecting tissue culture cells of these agents were compared with those of various toxic agents. Lt. damaged tissue culture cells at a lower concentration than its intravenous LD5o. Pt., on the other hand, affected cells at a higher concentration than its intravenous LD50. In addition, the cytopathological findings were compared with those induced by other agents in tissue culture cells.