RESUMEN
Speech processing entails a complex interplay between bottom-up and top-down computations. The former is reflected in the neural entrainment to the quasi-rhythmic properties of speech acoustics while the latter is supposed to guide the selection of the most relevant input subspace. Top-down signals are believed to originate mainly from motor regions, yet similar activities have been shown to tune attentional cycles also for simpler, non-speech stimuli. Here we examined whether, during speech listening, the brain reconstructs articulatory patterns associated to speech production. We measured electroencephalographic (EEG) data while participants listened to sentences during the production of which articulatory kinematics of lips, jaws and tongue were also recorded (via Electro-Magnetic Articulography, EMA). We captured the patterns of articulatory coordination through Principal Component Analysis (PCA) and used Partial Information Decomposition (PID) to identify whether the speech envelope and each of the kinematic components provided unique, synergistic and/or redundant information regarding the EEG signals. Interestingly, tongue movements contain both unique as well as synergistic information with the envelope that are encoded in the listener's brain activity. This demonstrates that during speech listening the brain retrieves highly specific and unique motor information that is never accessible through vision, thus leveraging audio-motor maps that arise most likely from the acquisition of speech production during development.
Asunto(s)
Percepción del Habla , Habla , Humanos , Percepción Auditiva , Acústica del Lenguaje , Lengua , LenguajeRESUMEN
Visual processing of other's actions is supported by sensorimotor brain activations. Access to sensorimotor representations may, in principle, provide the top-down signal required to bias search and selection of critical visual features. For this to happen, it is necessary that a stable one-to-one mapping exists between observed kinematics and underlying motor commands. However, due to the inherent redundancy of the human musculoskeletal system, this is hardly the case for multijoint actions where everyone has his own moving style (individual motor signature-IMS). Here, we investigated the influence of subject's IMS on subjects' motor excitability during the observation of an actor achieving the same goal by adopting two different IMSs. Despite a clear dissociation in kinematic and electromyographic patterns between the two actions, we found no group-level modulation of corticospinal excitability (CSE) in observers. Rather, we found a negative relationship between CSE and actor-observer IMS distance, already at the single-subject level. Thus, sensorimotor activity during action observation does not slavishly replicate the motor plan implemented by the actor, but rather reflects the distance between what is canonical according to one's own motor template and the observed movements performed by other individuals.
Asunto(s)
Encéfalo/fisiología , Excitabilidad Cortical/fisiología , Actividad Motora , Observación , Reclutamiento Neurofisiológico/fisiología , Adulto , Fenómenos Biomecánicos , Electromiografía , Femenino , Humanos , Individualidad , Masculino , Estimulación Magnética Transcraneal , Adulto JovenRESUMEN
BACKGROUND: In an attempt to clarify the role of gliadin toxicity in the pathogenesis of gluten intolerance (celiac disease), previous in vitro studies have been based on two-dimensional human cell cultures. However, the specific morphological and biochemical properties of in vivo tissue are better maintained in three-dimensional cell cultures (multicellular spheroids, MCS). The aim of this study was to develop a three-dimensional in vitro model to investigate the effects of gliadin on epithelial cells and broaden our understanding of the early tissue damage occurring in celiac disease. METHODS: The three-dimensionally growing Lovo cell line was exposed to increasing concentrations of peptic-tryptic-digested bread wheat gliadin (from 125 to 1000 microg/mL) for 7 days in order to evaluate cell viability (colony-forming assay), and at the standard concentration of 500 microg/mL for 7 days in order to evaluate MCS diameters, volumes and cell morphology using light and electron microscopy. RESULTS: In comparison with the controls, the cell viability of the gliadin-treated MCS was significantly reduced (20-80%), but there was no difference in size. Various degrees of cell damage (autophagic vacuoles and intra-cytoplasmic lipid-like droplets) were detected by both light and electron microscopy. CONCLUSION: This is the first study investigating the effects of gliadin on MCS. Lovo MCS seem to be responsive to gliadin exposure, thus confirming previous results obtained using two-dimensional cell cultures. The data suggest that three-dimensional cell cultures may be useful in broadening our understanding of some of the early effects of gliadin peptides on epithelial cells.
Asunto(s)
Enfermedad Celíaca/etiología , Gliadina/toxicidad , Esferoides Celulares/efectos de los fármacos , Adenocarcinoma/patología , Enfermedad Celíaca/patología , Línea Celular Tumoral/efectos de los fármacos , Tamaño de la Célula/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Neoplasias del Colon/patología , Relación Dosis-Respuesta a Droga , Humanos , Células Madre Neoplásicas , Esferoides Celulares/patología , Esferoides Celulares/ultraestructuraRESUMEN
The pathogenesis of celiac disease is not completely understood but, although the initial step of the process is still unclear, an altered immune response seems to play a major role. Previous studies of the biological properties of gliadin have highlighted its cytotoxic effects, and the aim of this study was to develop an in vitro technique to study them. The LoVo (human colon adenocarcinoma) cell line grown in two-dimensional cultures was exposed to different concentrations of digested bread wheat gliadin (62, 125, 250, 500 and 750 microg/ml) for 48 h, after which cell growth and oxidative balance (the content of reduced glutathione (GSH), and peroxidase, transferase and reductase activity) was evaluated. Other food proteins were used as controls. Our data revealed a statistically significant inhibition of cell growth in proportion to the gliadin concentration (from 26 to 100%), combined with a decrease in GSH content (-38% at 500 microg/ml) and reduced enzymatic activity (-30% at 500 microg/ml). The controls did not show any noxious effect. Our results confirm the usefulness of LoVo cells in evaluating gliadin cytotoxicity and that they can be used to investigate the biological properties of gliadin.
Asunto(s)
Adenocarcinoma/patología , Enfermedad Celíaca/fisiopatología , Neoplasias del Colon/patología , Gliadina/efectos adversos , División Celular , Relación Dosis-Respuesta a Droga , Glutatión/metabolismo , Humanos , Oxidorreductasas/farmacología , Peroxidasa/farmacología , Transferasas/farmacología , Células Tumorales CultivadasRESUMEN
Drug resistance, one of the major obstacle in the successful anticancer therapy, can be observed at the outset of therapy (intrinsic resistance) or after exposure to the antitumor agent (acquired resistance). To gain a better insight into the mechanisms of intrinsic resistance we have analyzed two human cell types derived from untreated tumors: MCF-7 breast cancer and A549 non small cell lung cancer (NSCLC). We have examined: the cytotoxic effect induced by doxorubicin (DOX); the time course of drug accumulation by flow cytometry and intracellular drug distribution by confocal microscopy; the expression and distribution of proteins related to anthracycline resistance, such as P-gp (P-glycoprotein), MRP1 (multidrug resistance-associated protein) and LRP (lung resistance-related protein). The cytotoxicity assays showed that A549 cells were less sensitive than MCF-7 cells to the DOX treatment in agreement with the different DOX uptake. Moreover, while in A549 cells DOX was mostly located in well defined intracytoplasmic vesicles, in MCF-7 cells it was mainly revealed inside the nuclei. The analysis of P-gp and MRP expression did not show significant differences between the two cell lines while a high expression of LRP was detected at the nuclear envelope and cytoplasmic levels in A549 cells. These findings suggest that the lower sensitivity to DOX treatment showed by lung carcinoma cells could be ascribed to drug sequestration by LRP inside the cytoplasmic compartments.
Asunto(s)
Antineoplásicos/farmacología , Neoplasias de la Mama/patología , Carcinoma de Pulmón de Células no Pequeñas/patología , Doxorrubicina/farmacología , Resistencia a Antineoplásicos/fisiología , Neoplasias Pulmonares , Proteínas de Neoplasias/farmacología , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/biosíntesis , Citoplasma/química , Femenino , Citometría de Flujo , Humanos , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/biosíntesis , Proteínas de Neoplasias/metabolismo , Células Tumorales Cultivadas , Partículas Ribonucleoproteicas en Bóveda/metabolismoRESUMEN
The 2 clones, LoVo 5 and LoVo 7, derived from untreated LoVo WT human colon adenocarcinoma cells and exhibiting different sensitivity to doxorubicin (DOX), were compared in order to identify possible determinants of intrinsic drug resistance. A multidrug resistant variant cell line, selected from LoVo WT cells by continuous exposure to DOX (LoVo DX), was also included in the study. Analysis of the expression and organization of cytoskeletal elements by flow cytometry and fluorescence microscopy evidenced a positive correlation between vimentin expression and DOX resistance in LoVo 7 and LoVo DX cells, whereas differences in actin, tubulin or cytokeratin did not seem to relate to drug response. The expression and localization of different drug transporters commonly implicated in drug resistance, i.e., the MDR1 gene product P-glycoprotein (P-gp), the multidrug resistance-related protein MRP and the lung resistance-related protein LRP were also investigated by means of flow cytometry and fluorescence microscopy, following labeling with specific monoclonal antibodies. Surface expression of P-gp was only detected in LoVo DX cells, which also exhibited increased MRP and LRP protein levels. However, significant amounts of P-gp were found at intracellular sites in the intrinsically resistant LoVo 7 clone. Modulation of P-gp function by cyclosporin A was found to alter DOX accumulation and efflux in LoVo 7 cells, indicating that intracellular P-gp plays a functional role in drug trafficking and suggesting possible implications in determining the intrinsic resistance displayed by this clone.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/biosíntesis , Adenocarcinoma/metabolismo , Neoplasias del Colon/metabolismo , Resistencia a Múltiples Medicamentos/fisiología , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Transportadoras de Casetes de Unión a ATP/metabolismo , Adenocarcinoma/patología , Antineoplásicos/farmacocinética , Antineoplásicos/farmacología , Western Blotting , Neoplasias del Colon/patología , Proteínas del Citoesqueleto/biosíntesis , Proteínas del Citoesqueleto/metabolismo , Citoesqueleto/metabolismo , Citoesqueleto/fisiología , Doxorrubicina/farmacocinética , Doxorrubicina/farmacología , Resistencia a Antineoplásicos , Ensayos de Selección de Medicamentos Antitumorales , Citometría de Flujo , Humanos , Inmunohistoquímica , Microscopía Electrónica de Rastreo , Microscopía Fluorescente , Proteínas Asociadas a Resistencia a Múltiples Medicamentos , Proteínas de Neoplasias/metabolismo , Fenotipo , Pruebas de Precipitina , Células Tumorales Cultivadas/efectos de los fármacos , Partículas Ribonucleoproteicas en Bóveda/metabolismoRESUMEN
The aim of the present paper was to analyse the effect of long-term inhibitory treatment, for at least 7 days, of individual protein kinase C (PKC) isoforms on the survival of LoVo human colon adenocarcinoma cells to doxorubicin exposure. The treatment for 2 h, after plating the cells, and after 3 days with 1 microM Gö6976, a specific inhibitor of protein kinase C (PKC)-alpha and -betal isoforms, induced on day 7 in LoVo cell lines (WT) a significant increased survival when these cells were exposed to increasing doxorubicin concentrations. In contrast, resistant LoVo cells (DX) did not show significant changes in the survival to doxorubicin exposure when incubated with the inhibitor of the same specific PKC isoforms. In addition, Gö6976 reduced the PKC-alpha activity (the main calcium-dependent PKC isoforms expressed) in both cell lines with contemporary increased expression. Under such conditions, an increased nuclear activity and an increased P-glycoprotein expression occurred only in WT-treated cells with respect to untreated cells. Taken together, our data indicate a specific relationship between PKC-alpha inhibition, the increased nuclear PKC-alpha activity as well as the increased expression of P-glycoprotein, possibly causing the acquisition of a resistant phenotype in WT LoVo cells.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/biosíntesis , Adenocarcinoma/patología , Antineoplásicos/farmacología , Neoplasias del Colon/patología , Doxorrubicina/farmacología , Proteína Quinasa C/efectos de los fármacos , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/efectos de los fármacos , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Supervivencia Celular , Neoplasias del Colon/genética , Neoplasias del Colon/metabolismo , Resistencia a Antineoplásicos , Regulación Neoplásica de la Expresión Génica , Humanos , Isoenzimas , Fenotipo , Proteína Quinasa C/metabolismo , Células Tumorales CultivadasRESUMEN
A new in vitro method to evaluate the early critical interactions between synthetic prosthetic materials and growing tissues is reported. The correct spatial organization and proper cell to cell interaction required to mimic the in vivo environment was obtained in a 3-dimensional (3-D) embryo organ culture. The clot formed by plasma and chick-embryo extract provided a natural 3-D extracellular matrix that was able to support the growth and differentiation of intestinal tissue dissected from 12-day-old chick embryos. Different materials used for the repair of abdominal wall defects were taken as standards; all the prosthetic materials were devoid of any evident cytotoxic potential over a 10-day culture period, so they did not interfere with the organogenesis process. A polyglactin mesh (Vicryl) was fully incorporated into the growing tissue, but early signs of its degradation were detectable. The biologically inert materials polyethylene terephthalate (Mersilene) and polypropylene (Marlex, Prolene, and Herniamesh) retained their structural integrity when incubated with cultured tissue at 37 degrees C, and they did not hinder cellular proliferation or fibroblast migration. However, the outgrowth behavior was very different while the connective tissue invaded the interstices of the polyethylene terephthalate mesh; the explants and the migrating cells were repelled by hydrophobic polypropylene meshes. These findings are in agreement with other reported results in in vivo studies. Therefore, this method can be considered as reliable and predictable for the evaluation of biopolymers.
Asunto(s)
Músculos Abdominales/cirugía , Materiales Biocompatibles , Animales , Embrión de Pollo , Modelos Biológicos , Técnicas de Cultivo de ÓrganosRESUMEN
Intrinsic low-level resistance to anti-cancer drugs is a major problem in the treatment of gastrointestinal malignancies. To address the problem presented by intrinsically resistant tumours, we have isolated two monoclonal lines from LoVo human colon adenocarcinoma cells: LoVo/C7, which is intrinsically resistant to doxorubicin (DOX); and LoVo/C5, which shows the same resistance index for DOX as the mixed parental cell population. For comparison, we have included in the study a LoVo-resistant line selected by continuous exposure to DOX and expressing a typical multidrug resistant (MDR) phenotype. In these cell lines we have studied the expression and/or activity of a number of proteins, including P-glycoprotein 170 (P-gp), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), glutathione (GSH)-dependent enzymes and protein kinase C (PKC) isoforms, which have been implicated in anti-cancer drug resistance. Intracellular DOX distribution has been assessed by confocal microscopy. The results of the present study indicate that resistance in LoVo/C7 cells cannot be attributed to alterations in P-gp, LRP or GSH/GSH-dependent enzyme levels. Increased expression of MRP, accompanied by alterations in the subcellular distribution of DOX, has been observed in LoVo/C7 cells; changes in PKC isoform pattern have been detected in both intrinsically and pharmacologically resistant cells.
Asunto(s)
Adenocarcinoma/metabolismo , Neoplasias del Colon/metabolismo , Doxorrubicina/farmacología , Partículas Ribonucleoproteicas en Bóveda , Transportadoras de Casetes de Unión a ATP/metabolismo , Células Clonales , Resistencia a Antineoplásicos , Citometría de Flujo , Glutatión/metabolismo , Proteínas Asociadas a Resistencia a Múltiples Medicamentos , Proteínas de Neoplasias/metabolismo , Proteína Quinasa C/metabolismo , Factores de Tiempo , Células Tumorales CultivadasRESUMEN
The efficacy of cosmetic products and active substances have been investigated on human keratinocytes cell line on a pool of tests. The work aimed to study the possible modifications of the biological parameters tested (cytotoxicity and cytoskeleton morphology) related to the cellular adhesion function. The results have permitted to define different activities, for the different products, compared to the untreated culture and to their placebo.
Asunto(s)
Cosméticos/toxicidad , Queratinocitos/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Medio de Cultivo Libre de Suero , Citoesqueleto/efectos de los fármacos , HumanosRESUMEN
We selected two clones, isolated from the human colocarcinoma cell line LoVo, showing a sensitivity to doxorubicin similar to (LoVo clone 5) or three times lower than (LoVo clone 7) the parental cell line. Since vimentin was atypically expressed in a human breast carcinoma cell line made resistant to doxorubicin, we looked at vimentin expression in these two clones with spontaneously different sensitivity to the drug. For comparison we used the parental cell line LoVo WT and LoVo/DX made resistant pharmacologically. mRNA for vimentin was undetectable by Northern blot analysis in LoVo WT and in LoVo clone 5, while expression of this gene was high in LoVo clone 7 and in LoVo/DX. This increase in mRNA levels was not related to an amplification of DNA, as suggested by Southern blot analysis. Immunofluorescence and immunocytochemistry findings confirmed, at protein level, the mRNA data. In LoVo clones 5 and 7, there were respectively 8.6% and 71% vimentin-positive cells, although the two clones showed similar expression of multidrug resistance gene 1 (mdr-1) and accumulated intracellular doxorubicin at similar levels. Similarly, drug efflux was the same for both clones. Our results show for the first time that cells resistant to doxorubicin express vimentin independently of the mdr glycoprotein. However when cells from clone 5 were transfected with human vimentin cDNA, they did not become resistant, indicating that vimentin can be considered as a marker of resistance in these cells but does not give rise to a resistant phenotype by itself.
Asunto(s)
Neoplasias Colorrectales/tratamiento farmacológico , Neoplasias Colorrectales/metabolismo , Doxorrubicina/farmacología , Vimentina/fisiología , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/fisiología , Células Clonales/química , Neoplasias Colorrectales/genética , ADN de Neoplasias/genética , Resistencia a Múltiples Medicamentos , Ensayos de Selección de Medicamentos Antitumorales , Expresión Génica , Humanos , ARN Mensajero/análisis , ARN Mensajero/genética , ARN Mensajero/metabolismo , Células Tumorales Cultivadas/efectos de los fármacos , Vimentina/biosíntesis , Vimentina/genéticaRESUMEN
A cell line, GBM, was established from a human malignant glioblastoma and was characterized with particular reference to its response to conventional drugs. The GBM cell line exhibited a 73 +/- 7 h doubling time in monolayer cultures. Expression of glial fibrillary acidic and S-100 proteins was observed. Karyotype analysis of GBM cells at early passages revealed the presence of two near-triploid clones (A and B) with multiple chromosome rearrangements; a 100% frequency for clone B was observed in the established cell line. GBM cells had tumorigenic properties, since the s.c. injection of cultured cells into nude mice gave rise to slowly growing tumors. The morphology of GBM cells was retained during in vitro and in vivo passages, as judged by light microscopy. GBM cells were relatively resistant to most conventional drugs; among the tested drugs, only taxol exhibited a marked cytotoxic effect comparable to that found in cells of a different tumor type. GBM cells were found positive for the epidermal growth factor receptor, HER2-neu and P-glycoprotein by flow cytometry of cells labelled with monoclonal antibodies. In spite of the expression of relatively high gamma-glutamyltransferase activity, the intracellular glutathione level was comparable to that of other chemosensitive tumor cells. This glioblastoma cell line is a suitable model for the identification and preclinical studies of new agents and provides an additional system to explore the molecular basis of the intrinsic drug resistance of glioblastoma.
Asunto(s)
Antineoplásicos/toxicidad , Glioblastoma/patología , Animales , Biopsia , Ciclo Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Línea Celular , Bandeo Cromosómico , Técnicas de Cultivo/métodos , Glioblastoma/genética , Glutatión/metabolismo , Humanos , Cariotipificación , Masculino , Ratones , Ratones Desnudos , Persona de Mediana Edad , Trasplante Heterólogo , Células Tumorales Cultivadas , gamma-Glutamiltransferasa/metabolismoRESUMEN
In order to investigate the involvement of Protein Kinase C (PKC) in the signal transduction mechanisms related to intrinsic chemoresistance, two cellular clones were isolated from LoVo/WT colon adenocarcinoma cell line and their cytogenetic pattern was studied: LoVo C1.7 was intrinsically resistant to Doxorubicin while LoVo C1.5 showed the same resistance index as the mixed parental cell population. Two PKC isoforms, immunologically identified as beta and alpha PKC, were isolated from the cytosolic fraction of all cell types and one single peak of alpha PKC was obtained from the particulate fraction. Resistant LoVo C1.7 cells showed a significant increase of PKC activity; preincubation with H-7 induced PKC inhibition and reversal of drug resistance. These data suggest that in our cell system the identified calcium-dependent PKC subtypes can play a role in the mechanisms of intrinsic resistance.
Asunto(s)
Calcio/farmacología , Doxorrubicina/toxicidad , Resistencia a Medicamentos , Isoenzimas/metabolismo , Isoquinolinas/farmacología , Piperazinas/farmacología , Proteína Quinasa C/metabolismo , 1-(5-Isoquinolinesulfonil)-2-Metilpiperazina , Adenocarcinoma , Supervivencia Celular/efectos de los fármacos , Cromatografía , Aberraciones Cromosómicas , Neoplasias del Colon , Citosol/enzimología , Durapatita , Humanos , Hidroxiapatitas , Isoenzimas/antagonistas & inhibidores , Isoenzimas/aislamiento & purificación , Cariotipificación , Proteína Quinasa C/antagonistas & inhibidores , Proteína Quinasa C/aislamiento & purificación , Células Tumorales Cultivadas , Ensayo de Tumor de Célula MadreRESUMEN
Acquired or spontaneous resistance is a major clinical problem in the treatment of cancer. Low levels of MDR gene expression or P-glycoprotein have been correlated with a high level of drug resistance in vitro and a poor response to chemotherapy in some tumors. A strong correlation between MDR mRNA, P-glycoprotein levels and degree of drug resistance has not been found in several resistant model tumor cell lines. In some cell lines at low and high level of resistance different mechanisms seem to be involved.
Asunto(s)
Proteínas Portadoras/metabolismo , Resistencia a Medicamentos/genética , Expresión Génica , Glicoproteínas de Membrana/metabolismo , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP , Antineoplásicos/metabolismo , Antineoplásicos/uso terapéutico , Antineoplásicos/toxicidad , Proteínas Portadoras/biosíntesis , Proteínas Portadoras/genética , Línea Celular , Supervivencia Celular/efectos de los fármacos , Humanos , Glicoproteínas de Membrana/biosíntesis , Glicoproteínas de Membrana/genética , Neoplasias/tratamiento farmacológico , Neoplasias/genética , ARN Mensajero/metabolismo , Células Tumorales CultivadasRESUMEN
Two sublines of the ovarian reticular cell sarcoma M5 in C57BL mice respond differently to cyclophosphamide and other alkylating agents. The subline R16, which is resistant to cyclophosphamide, was obtained by treating M5 mice repeatedly with this compound and subsequently transplanting the regrowing tumor for 16 passages. The R16 subline shows biological characteristics perfectly superimposable to those of the parent line and histologically resembles an undifferentiated mesenchymal neoplasia with numerous atypical nuclei and karyokinetic figures with large necrotic areas. The cytogenetic examination of the distribution in the chromosomal number of R16 indicates that this subline may be considered a clone of the parent line with a modal class of 35 chromosomes (34-37) versus a class of 34 (31-37) in the M5 tumor line. The presence of metacentric chromosomes characterizes the modal class of the two lines, 23 in the R16, and 25 in the M5 tumor lines.
RESUMEN
In the present study, the biodisposition of 4-demethoxydaunorubicin (4DDM) and its 13-dihydrometabolite was compared with daunorubicin (DM) and its metabolite in rabbit serum, and the results were considered in the light of this DM analog's pharmacokinetic behavior in mice. In rabbit serum, the levels of the 13-OH derivative of both DM and 4DDM (daunorubicinol and 4-demethoxydaunorubicinol) were higher than in mice. In vitro metabolic studies with mouse and rabbit cytosol indicated that the hepatic metabolism was quantitatively important for both analogs (70%-90% for DM and 4DDM was reduced to the 13-OH metabolite), but the rabbit had a much higher specific capacity to metabolize these compounds. DM seemed a better substrate for cytoplasmic aldoketoreductase, the enzyme affinity in rabbits being three times higher than for 4DDM. Cytotoxicity studies in vitro showed that 4-demethoxydaunorubicinol, unlike daunorubicinol, was as cytotoxic as the parent compound, and this suggests this metabolic step does not inactivate 4DDM but contributes to its high and long-lasting biological activity in vivo.