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L Y Yang

Publications and source records attributed to L Y Yang.

At least 73 records · Page 4Linked to original sources
PubMed1990

Lipolysis of menhaden oil triacylglycerols and the corresponding fatty acid alkyl esters by pancreatic lipase in vitro: a reexamination.

In order to distinguish between possible fatty acid differences during lumenal lipolysis and cellular absorption, we have reinvestigated the in vitro hydrolysis of menhaden oil and its alkyl esters by pancreatic lipase. For this purpose we incubated menhaden oil or its fatty acid methyl and ethyl esters with porcine pancreatic lipase in the presence of bile salts and determined the composition of the released free fatty acids, monoacylglycerols, diacylglycerols, and residual triacylglycerols, or the free fatty acids and residual alkyl esters, respectively, by thin-layer and gas-liquid chromatography. There was significant discrimination against the delta 4- to delta 7-unsaturated fatty acids of both medium and long chain lengths during the hydrolysis of menhaden oil and its fatty acid ethyl esters. In general, the ethyl esters were hydrolyzed 10-50 times more slowly than the corresponding glyceryl esters, depending on the exact ratio of the two substrate types. None of the triacylglycerols or ethyl esters, however, was completely resistant to hydrolysis resulting in an eventual cleavage of all the alkyl esters and presumably all the primary ester bonds in the triacylglycerol molecules. Since the rate of release of the least resistant fatty acid exceeded that of the most resistant acid by only a factor of 6, it is concluded that in the presence of a large excess of lipase the liberated fatty acids would approach the composition of the dietary alkyl or glyceryl esters, as observed during lumenal lipolysis (Yang, L.-Y., A. Kuksis, and J. J. Myher. 1989. Biochem. Cell Biol. 67: 192-204).

Animals↗
PubMed1988

Increased cytotoxicity and reversal of resistance to cis-diamminedichloro-platinum(II) with entrapment of cis-Bis-neodecanoato-trans-R,R-1,2-diaminocyclohexaneplatinum (II) in multilamellar lipid vesicles.

The role of liposome entrapment in modulating the cytotoxicity of a lipophilic cisplatin derivative was assessed. cis-Bis-neodecanoato-trans-R,R-1,2-diaminocyclohexaneplatinum++ +(II) (NDDP) was tested in suspension (free NDDP) or entrapped in multilamellar vesicles composed of dimyristoylphosphatidyl choline and dimyristoylphosphatidyl glycerol (L-NDDP). Against LoVo colon carcinoma cells sensitive to cisplatin, L-NDDP was two times more cytotoxic in vitro than free NDDP and cisplatin (Do 7 microM for L-NDDP, 15 microM for free NDDP, and 16 microM for cisplatin). Against LoVo cells resistant to a concentration of 3 micrograms/ml of cisplatin, L-NDDP was three times more cytotoxic than free NDDP and cisplatin (Do 14 microM for L-NDDP, 45 microM for free NDDP, and 48 microM for cisplatin). In in vivo studies, free NDDP was less potent and less active than L-NDDP against i.p. L-1210 leukemia (free NDDP, optimum %T/C 148 at a dose of 75 mg/kg; L-NDDP, optimum %T/C 185 at a dose of 25 mg/kg) and i.p. L1210/PDD leukemia (free NDDP, optimum %T/C 128 at a dose of 50 mg/kg on Days 1, 5, and 9; L-NDDP, optimum %T/C 200 at a dose of 12.5 mg/kg on Days 1, 5, and 9). Free NDDP administered i.v. was inactive against liver metastases of M5076 reticulosarcoma (%T/C 102) while L-NDDP showed significant activity (%T/C 140). The single dose i.v. LD50 in mice of free NDDP and L-NDDP were similar (79.4 mg/kg for free NDDP and 64.5 mg/kg for L-NDDP). These studies show that NDDP is a liposome-dependent drug since it can only be satisfactorily formulated in the liposomal form and since the liposomal carrier plays a crucial role in determining its antitumor activity.

Animals↗
PubMed1987

Size and composition of lymph chylomicrons following feeding corn oil or its fatty acid methyl esters.

Male rats with thoracic duct cannulae were intubated with corn oil or fatty acid methyl esters and the lymph was collected over the next 2-72 h. The apoprotein (apo) composition of the chylomicrons, isolated by conventional ultracentrifugation, was determined by sodium dodecyl sulfate - polyacrylamide - glycerol gel electrophoresis and isoelectric focusing. The lipid content and composition was assessed by gas--liquid chromatography. The particle size was obtained by calculation and confirmed by electron microscopy. The study demonstrates that both the monoacylglycerol (corn oil feeding) and the phosphatidic acid (methyl ester feeding) pathways of triacylglycerol biosynthesis yield chylomicrons with closely similar apoprotein profiles representing apo B-48, apo A-IV, apo E, apo A-I, and the apo C components. A protein band corresponding to apo B-100 was occasionally observed as a minor component of the chylomicrons from both groups of animals. The chylomicrons from corn oil feeding had about two times larger diameters than those from methyl ester feeding. There were no significant differences in the composition of the apoproteins, although the smaller particles had two times higher apoprotein/triacylglycerol ratios. It was calculated that the amount of apo B per lipid particle for the ester fed rats ranged from one to eight molecules and was closely correlated with the particle size. The corn oil fed rats yielded about three molecules apo B per lipid particle regardless of the particle size. It is concluded that the pathway of intestinal triacylglycerol biosynthesis has a significant effect on the apoprotein mass and to a lesser extent on the apoprotein and lipid composition of the chylomicrons. The phosphatidic acid pathway produces smaller particles and transfers to the bloodstream twice as much apoprotein per gram of fat than the monoacylglycerol pathway, which yields the larger particles. Possible variations in the site and rate of biosynthesis of the triacylglycerols could not be entirely excluded as contributing factors.

Animals↗
PubMed1987

Stereochemical course of intestinal absorption and transport of mustard-seed oil triacylglycerols in the rat.

Male rats with thoracic duct cannulae were intubated with mustard-seed oil or the corresponding fatty acid methyl esters and the lymph was collected over 0-24 h. The chylomicron and very low density lipoprotein fractions were obtained by conventional ultracentrifugation. The triacylglycerols and glycerophospholipids were isolated and the positional distribution and molecular association of fatty acids were determined by stereospecific and chromatographic methods. The oleic, linoleic, and linolenic acids were recovered in the lymph in the proportion in which they occurred in the fat fed, while eicosenoic, erucic, and lignoceric acids were rejected to about the same extent by the two pathways of intestinal triacylglycerol biosynthesis. It is shown that the lymph triacylglycerols arising via the monoacylglycerol or the phosphatidic acid pathway possess structures that are closely similar to each other and to that of the original mustard-seed oil. It is proposed that this is a result of comparable fatty acid and positional specificity of the acyltransferases associated with the acylglycerol synthesis in the animal and plant tissues and the wide range of fatty acid chain lengths in the mustard-seed oil.

Animals↗
PubMed1986

The activity of flavone acetic acid (NSC 347512) on human colon cancer cells in vitro.

Flavone acetic acid (FAA) was incubated for 1 to 48 hr with 3 established human colon cancer cell lines endowed with distinct degrees of phenotypic properties. All 3 lines responded to FAA in almost identical fashion; when incubated with the drug for only 1 hr, an initial decrease in survival was observed for concentrations of 250 micrograms/ml but no further increments in cytotoxicity were elicited when the concentration of FAA was augmented. Increasing the length of treatment yielded relatively modest increments (about 1 log) in cell killing only after an interval of 48 hr and only at the highest concentration (1000 micrograms/ml). Because of these relatively poor cytotoxic effects and because the therapeutic range of FAA is so narrow, we conclude that this agent will not be a valuable contribution to the antitumor arsenal, at least for colon cancer.

Antineoplastic Agents↗
PubMed1986

Ligands of second generation platinum analogs decrease both platinum-induced DNA cross-linking and its ability to interact with 1-beta-D-arabinofuranosyl cytosine to potentiate cytotoxic efficacy.

We evaluated the cytotoxic and DNA cross-linking (CL) ability of four second generation platinum coordination complexes (TNO-6, JM-89, JM-8 and JM-9) delivered alone or in combination with 1-beta-D-arabinofuranosyl cytosine (ara-C) to human colon cancer cells (LoVo). Cell survival varied markedly as a function of the particular substitution moiety. JM-8 and JM-9 were virtually ineffective, even at concentrations as high as 50 micrograms/ml. At that concentration cis-diamminedichloroplatinum(II) (cis-DDP) killed greater than 99.99% of the cells. JM-82 was slightly more active while TNO-6 was the only derivative with appreciably higher cytotoxic activity due to an abrogation of the shoulder region of the type C survival curve. The highest CL effect was observed for cis-DDP followed closely by TNO-6. Very little CL effects were demonstrated for the other three analogs JM-82, JM-8 and JM-9 when measured 6 h after treatment. The combination of cis-DDP and ara-C augmented 10-fold the cytotoxic activity of cis-DDP alone, an effect accompanied by an almost 2-fold increase in CL; every other analog failed to interact in a potentiating manner (either cytotoxicity, or CL at 6 h) with the antimetabolite. Thus, it appears clear that the associated moieties of the Pt coordination complex play a fundamental role in reducing the interaction of the analogs with DNA (as reflected by the decreased CL and cytotoxic effects produced by each agent alone) and in totally preventing their interaction with ara-C to yield a potentiating lethal effect.

Carboplatin↗
PubMed1986

New monoclonal antibodies against colon cancer-associated antigens.

Established human colon cancer cells with distinct degrees of differentiation (LoVo, well-differentiated; SW620, intermediate differentiation; and SW1116, poorly differentiated) were used to produce monoclonal antibodies (MoAbs) by standard hybridoma techniques. Specificity was tested by an enzyme-linked immunosorbent assay against human foreskin cells, 7 established human colon cancer lines, a panel of 17 established human tumor lines of different histological origins, purified carcinoembryonic antigen, panels of red blood cells, and a suspension of lymphocytes obtained from 30 random normal donors. MoAb LoVo-F4 3E4/1A1/2E10 (MoAb F4/2E10) reacted with five colon cancer lines and only slightly with MCF-7 cells (estrogen receptor positive breast carcinoma). MoAb LoVo-F4 3E4/1A1/5C10 also reacted with the previous five colon cancer lines and with two gastric cancer lines. A MoAb obtained with a LoVo 3 M KCl membrane extract reacted exclusively with LoVo cells. MoAb SW620-F1 4E5/1A3 reacted with only three colon cancer cell lines and an estrogen receptor negative breast cancer line. MoAb SW1116-F2 1E3/1A1 reacted with four colon carcinoma cell lines, one gastric cancer line, MCF-7 cells, and a lung cancer line. MoAb SW1116-F2 1F3/1B1 reacted intensely with purified carcinoembryonic antigen and with every carcinoembryonic antigen-producing cell line available in our laboratory. Further studies concentrated on the immunoglobulin G1 MoAb F4/2E10. We demonstrated that the purified MoAb did not inhibit binding of MoAb CA19-9 to any colon Ca lines and reacted with fresh human colon carcinoma specimens regardless of whether they were processed by cryostat or paraffin embedding after fixation in formalin for 24 through 96 h. Using the peroxidase-antiperoxidase technique, MoAb F4/2E10 did not react with 23 normal adult and 18 fetal (less than 3 months old) human tissue specimens. When tested on 312 specimens of diverse histological origins and diseases, the MoAb was positive in 57 of 62 colorectal cancers, in 12 of 19 villous adenomas, in 5 of 7 adenomatous polyps, and in 10 of 12 cases of ulcerative colitis. With the exception of 2 of 15 cases of Crohn's disease that were slightly positive, all tissues from nonmalignant diseases (regardless of histological origin) were consistently negative. There was only weak reactivity in 2 of 18 breast cancers, 7 of 21 squamous cell carcinomas, 4 of 27 lung tumors, 1 of 13 kidney carcinomas and in 7 miscellaneous tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗
PubMed1985

Comparative cytotoxicity between cisplatin and second generation platinum analogs.

The cytotoxic activity of cis-DDP and four second generation platinum coordination complexes (TNO-6; JM-82; JM-8; and JM-9) was compared on six established human colon carcinoma cell lines with different degrees of differentiation. Cytotoxicity was evaluated by the inhibition of colony formation technique. Cis-DDP was uniformily active against all lines. JM-8 and JM-9 were virtually ineffective for all cell lines, even at concentrations as high as 50 micrograms/ml. JM-82 was slightly more active although (with the exception of LoVo cells) still about 10-fold less efficacious than cis-DDP. TNO-6 was the only derivative with appreciable cytotoxic activity although about 2 to 5-fold less than cis-DDP for lines SW48, 620, 480, and 1116. For LoVo and SW403, TNO-6 was slightly more active than cis-DDP. In both such instances, increased efficacy resulted from abrogation of the shoulder region of the survival curve while the slope remained essentially intact. Thus any enhancement in therapeutic efficacy with these second generation analogues can only be expected from possible decreases in toxic effects but not from superior tumor cell kill activity.

Antineoplastic Agents↗
PubMed1985

The synergistic lethal interaction of cis-diamminedichloroplatinum and natural nucleosides is related to increased DNA cross-links.

Human tumor cells were treated in vitro with combinations of cis- or trans-dichlodiammineplatinum (DDP) and natural nucleosides (thymidine, uridine, cytidine and adenosine). Effects were measured by inhibition of colony-formation (cell survival) and DNA alkaline elution (DNA cross-links). No increments in cell lethality or DNA cross-links were elicited by any combination of trans-DDP and nucleosides. In contrast, every combination of cis-DDP and nucleoside was eminently synergistic with 5- and 10-fold increases in cell lethality over the predicted sum of each agent alone. These increments in cell kill correlated linearly with increases in DNA crosslinks suggesting that the nucleosides interact with cis-DDP to enhance its cytotoxic crosslinking mode of action.

Adenosine↗
PubMed1985

Cytotoxic efficacy of reconstituted and stored antitumor agents.

The stability of the cell-killing efficacy of 10 antitumor drugs stored at different temperatures and concentrations was evaluated on an established human colon carcinoma cell line using the colony formation technique. Drugs were reconstituted in the appropriate solvent, further diluted in 0.9% NaCl solution to obtain the desired storage concentration, and stored at 4 degrees C, -20 degrees C, and -70 degrees C for periods of up to 3 weeks. Cytotoxic efficacy was tested weekly by exposing the cells to the final drug dilution for 1 h at 37 degrees C. Stability of cytotoxic potency depended on the particular drug, and the duration, concentration, and temperature of storage but, in general, most drugs remained efficacious only within limited periods of time (at most, 2 weeks). These results suggest that the conditions of drug storage following reconstitution are critical factors with respect to lethal efficacy. Therefore, analysis of in vitro cytotoxic efficacy can be meaningful only when storage conditions are specified in order to avoid false-negative results in the human tumor clonogenic assay.

Antineoplastic Agents↗
PubMed1985

Cellular basis for the inefficacy of 5-FU in human colon carcinoma.

Five established human colorectal carcinoma cell lines with distinct phenotypic properties were exposed to different concentrations of 5-FU for varying time intervals. Effects were measured by sequential cell counts and by inhibition of colony formation. Treatment for 1 hr with 1 microgram/ml barely decreased survival of all cell lines as measured by colony formation; at a concentration of 100 microgram/ml, survival was modestly reduced for all cell lines, and for concentrations of 1000 microgram/ml, survival was decreased by greater than 50%. Extending the length of the treatment interval markedly increased the degree of cell kill for all concentrations of 5-FU. Treatment for greater than 24 hrs resulted in almost complete extermination of colony-forming cells, even for relatively resistant cell lines. The effect of 5-FU treatment on cell number was more complex and depended on drug concentration, length of treatment, and type of cell line. In general, decrements in cell numbers were somewhat related to both drug concentration and length of treatment interval, especially if performed 7 days after terminating drug treatment. Earlier cell counts were inconclusive and the same result could be obtained for different drug concentrations or treatment intervals. Furthermore, these results would change on a daily basis. More important, cell count results never correlated with the survival endpoint measured by inhibition of colony formation. Our results suggest that enhancement of the currently poor performance of 5-FU in the treatment of human colon carcinoma could originate from changing the administration modality to long-term infusion.

Cell Count↗
PubMed1984

Cultured human tumour cells may be arrested in all stages of the cycle during stationary phase: demonstration of quiescent cells in G1, S and G2 phase.

Six human colon carcinoma cell lines were induced to enter stationary phase of growth by nutrient deprivation and cell crowding. Growth kinetics parameters (cell number, flow cytometric analysis of DNA distribution, and labelling and mitotic indices) were measured sequentially for all lines during the various stages of in vitro growth. Our results demonstrated that a substantial fraction of cells (9-18%) were located in G2 phase when they changed from an exponential to a stationary mode of growth. Moreover, a large number of cells in stationary phase of growth had an S-phase DNA content, as determined by flow cytometry, but failed to incorporate radioactive DNA precursors (up to 15-fold difference). To substantiate these findings, cells in stationary phase of growth were induced to enter exponential growth by re-seeding in fresh medium at a lower density. Subsequently observed changes in DNA-compartment distribution, and in labelling and mitotic indices were those expected from cells that had been arrested at different stages of the cycle during their previous stationary phase. Thus, the non-proliferating quiescent state (Q), traditionally located 'somewhere' in G1 phase, appears to be composed also of cells that can be arrested at other stages of the cycle (Qs and QG2). Although the proportion of such cells is rather small, their contribution to the growth kinetics behaviour of human in vivo tumours will become apparent following 'recruiting' or 'synchronizing' clinical manoeuvres and will prevent the formation of a clear-cut wave of synchronized cells.

Cell Cycle↗
PubMed1984

Cellular discriminants for a biological classification of human colon carcinoma.

We categorized established human colon carcinoma cell lines into three biological groups. Our studies were performed on six colorectal cancer lines representing the proposed three groups. Group I consisted of two lines designated LoVo and SW 48; Group II comprised two lines called SW 480 and SW 620; and Group III was represented by lines SW 403 and SW 1116. Group I consisted of the most differentiated cells. This differentiation encompassed morphological markers, gland and signet ring formation, and ciliary development. The outstanding morphological characteristic of Group III was the development of numerous multinucleated giant cells. The range and modal chromosome number increased from Group I to Group III, a change reflected by the higher DNA content of these cells as measured by flow cytometry. Carcinoembryonic antigen synthesis was maximal for Group III and virtually absent for Group II. The number of clonogenic cells decreased from Group I to Group III, while the proportion of nonproliferating cells calculated both by experiments using continuous labeling with tritiated thymidine, and by the primer-available alpha-DNA polymerase index, increased from Group I through Group III. Another important cytokinetic difference was that Group I had an exponential cell cycle stage distribution not seen for the other groups. Cells in Group I were easily propagated in athymic (nude) rats by s.c. injection; cells in Group II injected s.c. grew for about 30 days and then regressed spontaneously. Cells in Group III could only be grown when inoculated intracerebrally. Thus, our studies have now confirmed and extended the hypothesis that cultured human colorectal carcinomas can be separated into at least three groups on the basis of morphological differentiation, chromatin distribution, carcinoembryonic antigen production, cytokinetic properties, and xenograft propagation. Perhaps this classification is just the tip of the iceberg, and future studies will determine the existence of additional groups or subgroups on the basis of other markers. However, at present it appears established that malignant cells with a common histological origin in the gut express their phenotypic potential in a sufficiently discrete manner as to permit their classification into distinct biological groups. Thus, the stage is set for extrapolating this in vitro classification for an in vivo segregation of human colorectal tumors into categories with specific properties and diverse prognosis.

Animals↗
PubMed1983

The lethal activity and repair inhibition capacity of 1-(2-chloroethyl)-3-(2,6-dioxo-3-piperidyl)-1-nitrosourea (NSC 95466, PCNU), a nitrosourea with low carbamoylating activity.

The survival response of human colorectal carcinoma cells treated in vitro for 1 h with PCNU was characterized by a threshold exponential curve, Dq = 8 micrograms/ml (1 h) and Do = 22 micrograms/ml (1 h). Continuous treatment induced decreasing degrees of cell kill although PCNU was biologically stable in solution for at least 24 h. Cells treated with PCNU were unable to recover from potentially lethal damage but were quite capable of repairing PCNU-induced sublethal damage. Thus, PCNU with different alkylating and carbamoylating than other nitrosourea congeners had similar cytotoxic and repair inhibition capacities. Any therapeutic gain in the clinical use of PCNU must derive only from its lipophilic properties and not from its superior activity at the cellular level.

Antineoplastic Agents↗
PubMed1983

Comparative cytotoxicity of bisantrene, mitoxantrone, ametantrone, dihydroxyanthracenedione, dihydroxyanthracenedione diacetate, and doxorubicin on human cells in vitro.

The cytotoxic efficacies of several substituted anthraquinones, ametantrone, dihydroxyanthracenedione, dihydroxyanthracenedione diacetate, mitoxantrone, bisantrene, and doxorubicin, were evaluated on an established human colon adenocarcinoma cell line by the method of inhibition of colony formation. The concentration-dependent survival curve following treatment for 1 hr was biphasic exponential for all agents. At concentrations below 1 microgram/ml, mitoxantrone was about twice as active as both hydroxyl-substituted anthracenediones and doxorubicin, about 14 times more efficacious than ametantrone, and about 22 times more powerful than bisantrene. At higher concentrations, these differences in efficacy became even more pronounced. Treatment in stationary phase decreased the lethal efficacy of doxorubicin but not that of the other agents. No recovery of potentially lethal or sublethal damage was noted for any agent, but for anthracenedione derivatives, there was a small but statistically significant increase in cell kill during fractionated exposure. Continuous treatment with mitoxantrone or bisantrene resulted in marked degrees of cell killing, reaching 99.95 and 99.5%, respectively, after 24 hr. For doxorubicin, cell kill efficacy declined after 4 hr. Mitoxantrone was 10-fold more active on cells in G2 phase than on those in mid- to late-S phase. Sensitivity in G1 phase was intermediate. Thus, mitoxantrone appears as the most active compound while bisantrene and ametantrone are the least active agents. The cytotoxic efficacy of bisantrene increases during prolonged continuous exposure, while that of mitoxantrone increases in fractionated administration. These characteristics could be exploited in clinical strategies designed to improve the performance of these agents.

Anthracenes↗
PubMed1982

Lethal activity and kinetic response of cultured human cells to 4'-(9-acridinylamino)methanesulfon-m-anisidine.

Cytotoxic and cytokinetic effects of 4'-(9-acridinylamino)methanesulfon-m-anisidine (m-AMSA) were studied on a cultured human colon carcinoma and on a human lymphoma (T1) cell line. Proliferating cells were more susceptible (10-fold) to the cytotoxic effect of m-AMSA than were nonproliferating cells. The agent had minimal effects on DNA synthesis. At comparable exposure doses on m-AMSA, the degree of lethal cell damage exceeded inhibition of DNA synthesis by 4-fold. Cells synchronized in different stages of the cell cycle were equally sensitive to the cytotoxic effects of the drug, although the major cytokinetic effect was a block in G2. A greater killing effect was obtained by fractionated delivery than by a comparable dose delivered at one. These results suggest that superior antitumor results may be achieved by adequately spaced low doses of m-AMSA in the treatment of sensitive human tumors.

Aminoacridines↗
PubMed1981

Differential killing efficacy of twenty antitumor drugs on proliferating and nonproliferating human tumor cells.

The lethal effects of a 1-hr treatment with 20 antitumor drugs on proliferating and nonproliferating cultured human colon carcinoma cells (line LoVo) were analyzed quantitatively by the colony-forming technique. Proliferating cells were obtained from exponentially growing cultures, while nonproliferating cells were from cultures in a stationary phase of growth. The 1-hr treatment was intended to approximate serum peak levels after bolus administration. Two agents, cis-platinum and vindesine, were more effective on nonproliferating than on proliferating cells. Mitomycin C, nitrosourea, and dihydroxybisalkylanthracenedione were equally effective on proliferating and nonproliferating cells. The low lethal activity (less than 1 log) of methylglyoxal bis(guanylhydrazone), hycanthone, and vinblastine was similar in proliferating and nonproliferating cells. For most drugs (Adriamycin, rubidazone, bleomycin, maytansine, vincristine, epipodophyllotoxin, fluorouracil, hydroxyurea, methotrexate, and transplantinum) cytotoxicity was significantly less pronounced (or even totally absent) in nonproliferating than in proliferating cells. These results demonstrate the significance of cellular proliferation kinetics in determining sensitivity to antitumor therapy. Nonproliferating human cells have decreased sensitivity to most antitumor agents. An occasional agent may present increased activity to nonproliferating cells; but at best, few agents can be expected to be as effective on nonproliferating as on proliferating cells.

Animals↗