Hypersensitivity reactions to the Sabin vaccine in children with cow's milk allergy.

BACKGROUND: The Sabin vaccine is used world-wide, and most children with food allergies receive it without incident. However, in the 2009 vaccination campaign conducted in Argentina, four children experienced immediate-type hypersensitivity reactions following vaccination. OBJECTIVE: We aimed to review the medical history of the affected children, study their allergic condition after the episodes and analyse the presence of allergenic vaccine components. METHODS: Patients were selected based on their immediate allergic reactions following vaccination. They were assessed for allergies to cow's milk and hen's egg. The presence of cow's milk proteins in the vaccine was tested by various immunoassays involving cow's milk- or α-lactalbumin-specific polyclonal rabbit antiserum and patient sera. RESULTS: All of the patients had a history of milk allergy, and no history or current evidence of egg hypersensitivity was found. Levels of cow's milk- and Sabin vaccine-specific IgE were increased, and the result of a skin prick test with cow's milk proteins or the Sabin vaccine was positive in each patient. In addition, an ELISA using specific rabbit antiserum detected α-lactalbumin in the Sabin vaccine. When α-lactalbumin was employed as a soluble inhibitor in a competitive ELISA, binding to vaccine-coated plates by cow's milk- or α-lactalbumin-specific rabbit antiserum or by patient serum containing IgE was inhibited. CONCLUSIONS: We have demonstrated that these patients were allergic to cow's milk, and had circulating and mast cell-bound IgE antibodies specific to cow's milk proteins. We found that the Sabin vaccine contained α-lactalbumin, which may have been responsible for the reactions elicited following vaccination with the Sabin and dual viral vaccines in combination.

Alergia al huevo en Pediatría. Documento del Comité de Pediatría de la Asociación Argentina de Alergia e Inmunología Clínica / Egg allergy in pediatrics. Pediatric Committee document of the Argentina Association of Allergy and Clinical Immunology

El huevo de gallina es una fuente de proteínas de alto valor biológico de bajo costo y de vitaminas del complejo B, importantes para la alimentación del niño. Culturalmente es uno de los alimentos básicos de nuestra dieta y, debido a esto, la alergia a sus proteínas es una de las más frecuentes en la infancia y tiene su mayor impacto en niños en edad preescolar. Estos niños representan una población vulnerable debido a que se encuentran en una etapa importante de su crecimiento y desarrollo, y el tratamiento de esta patología genera la adopción de dietas restrictivas que pueden impactar en forma negativa en su salud y calidad de vida. Este impacto está dado en parte por la ubicuidad de sus proteínas, que limita ampliamente la dieta y genera riesgos de reacciones alérgicas que se incrementan a medida que el niño crece y alcanza una mayor independencia. Teniendo en cuenta la importancia de esta patología, el Comité de Pediatría realizó una revisión actualizada con el fin de proveer herramientas útiles para el manejo adecuado de la misma. (AU)

Eggs are a source of low cost high biological value protein and complex B vitamins important for the child's nutrition. Culturally it is one of the staples of our diet and because of this, egg allergy is one of the most common food allergies in childhood and has its greatest impact on preschool children. These children represent a vulnerable population because they are at an important stage in their growth and development and the treatment of this condition generates the adoption of restrictive diets that may impact negatively on their health and quality of life. This impact is given in part by the ubiquity of their proteins that largely restrict the diet and generates risks of allergic reactions that increase as the child grows and earns greater independence. Given the importance of this issue the Pediatrics Committee conducted an updated review to provide useful tools to manage this condition.(AU)

Estudio multicéntrico de evaluación del conocimiento de los pediatras acerca de reacciones alérgicas a vacunas para enfermedades infecciosas / A multicenter study assessing pediatrician's knowledge about allergic reactions to infectious disease vaccines

Resumen. Las reacciones alérgicas a las vacunas contra agentes infecciosos han generado preocupación entre los pediatras. Sin embargo, se desconoce el grado de información que tienen estos especialistas de nuestro país sobre este tema. Objetivo. Contar con datos estadísticos acerca de este problema. Población. Trescientos veinte pediatras encuestados. Método. Estudio multicéntrico descriptivo prospectivo de corte transversal realizado con encuestas estandarizadas Resultados. El 12,5% de los encuestados reconoció la presencia de síntomas de aparición rápida como reacción de hipersensibilidad inmediata. (61,6%) consideró a estas reacciones como infrecuentes. El 72,6% reconoció a la neomicina como causa de alergia, el 51,6 % al timerosal, el 73% a los conservantes, un 30,4% a la gelatina y la mitad de los encuestados al componente activo. El 62,3% reconoció a la proteína del huevo como componente de la vacuna MMR. Ante antecedentes de alergia al huevo, el 35% de los médicos contestó que contraindica siempre las vacunas que contienen proteína del huevo, el 14% no las contraindica nunca y el 9% no sabe. Los médicos de menos de 5 años de recibidos reconocieron con mayor frecuencia la presencia de una reacción alérgica a vacunas (p = 0,004). Los médicos de más de 10 años de recibidos solicitan más frecuentemente interconsulta con el especialista ante casos de vacunación de pacientes con alergia a la proteína del huevo (p = 0,01). Conclusiones. Existe un grado importante de desconocimiento acerca de las reacciones alérgicas a vacunas, los componentes de las vacunas involucrados en dichas reacciones y las conductas a tomar frente a pacientes con alergia al huevo.(AU)

Background: Allergic reactions to infectious disease vaccines have generated concern among pediatricians. It is unknown the level of pediatrician's knowledge about this issue. The aim of this study is to obtain statistical data about this issue in our country. Population: 320 pediatricians. Methods: A transversal prospective descriptive multicenter study by means of a survey. Results: 12.5% of participants were capable to identify symptoms of immediate hypersensitivity reactions and 61.6% considered that these reactions are not frequent. The pediatricians pointed out as the most commonly allergen components the following ones: Neomicine (72.6%), thymerosal (51.6 %), preservatives (73%), gelatin (30.4%) and active component (nearly 50%). 62.3% knew that eggs proteins are part of MMR vaccine. In the case of patient with history of egg allergy, 35% answered that they always contraindicate vaccination with egg protein vaccines while14% do not contraindicate and 9% do not know what to do. Physicians less than 5 years of graduation recognized more frequently the presence of allergic reactions (p: 0.004). Physicians with 10 or more years of graduation asked for specialist opinion more frequently in the case of patients with egg allergy (p: 0.01). Conclusions: It was found an important lack of information about allergic vaccine reactions, the involved vaccine constituents and the correct management of situations related to egg allergy.(AU)

Exposure to enriched environments increases brain nitric oxide synthase and improves cognitive performance in prepubertal but not in young rats.

Rats were randomly assigned to enriched (EE) or standard environments (SE) at 21 or 73 days of age, for 17 days. Half of the rats of each rearing condition were trained in a radial maze (RM). At 38 days (pre-pubertal) or 90 days (young), rats were sacrificed and brain cytosolic and mitochondrial nitric oxide synthase (mtNOS) activity was assayed. Western blot analysis of brain mtNOS was conducted. In the pre-pubertal group, EE rats improved their performance in the RM while SE rats did not. In the young group, SE and EE rats showed a random performance in the RM. In SE pre-pubertal rats, training increased brain cytosolic NOS and mtNOS activity by 68% and 82%. In EE non-trained pre-pubertal rats, brain cytosolic NOS and mtNOS activity increased by 80% and 60%, as compared with SE non-trained pre-pubertal rats. In EE pre-pubertal rats that were trained, brain cytosolic NOS and mtNOS activity increased by 70% and 90%, as compared with SE pre-pubertal rats that were not trained. A higher protein expression of brain mtNOS was found in EE rats, as compared with SE animals. Mitochondrial complex I activity was higher in EE than in SE rats. Training had no effect on complex I activity neither in SE nor in EE rats. In young rats, no significant differences in enzyme activities were found between EE and SE rats. These results support the hypothesis that brief exposure to EE and training produce effects on behavioral performance and on biochemical parameters in an age-dependent manner.

Influence of a semiochemical analogue on growing performances and meat quality of broilers.

Stress in broilers may have severe consequences on the final product quality. A synthetic analogue of uropygial secretion of mother hens was isolated from poultry. This mother hen uropygial secretion analogue (MHUSA) was tested in farm conditions on broilers during 12 wk. The purpose of this trial was to estimate the influence of MHUSA on growing performances, meat characteristics after processing, and stress indicators of broilers. After the 80-d period, birds under treatment were heavier at 3 different weighing ages (P

Citalopram concentrations and response in obsessive-compulsive disorder. Preliminary results.

OBJECTIVE: Citalopram, a highly potent SSRI, is effective in the treatment of depressive disorders and obsessive-compulsive disorder (OCD); however, very few studies have reported concentration-effect relationships for SSRIs. The aim of this study was to investigate the relationship between citalopram concentrations and clinical response in patients with OCD. METHODS AND STUDY DESIGN: Fifteen patients (aged 18-65 years) with a DSM-IV diagnosis of OCD were included in this open-label, single-blind study. Citalopram was started at a dosage of 20 mg/day; the dosage was increased to a maximum of 60 mg/day by the third week, on the basis of clinical need and tolerability. The dosage then remained unchanged until the end of the 10-week study. Clinical assessments were made at baseline, weekly for the first four weeks and then at weeks 6, 8 and 10. The assessment scales used were the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), the Clinical Global Impression Scale (CGI) and the Hamilton Depression Rating Scale (HDRS). Plasma citalopram concentrations were determined using a high performance liquid chromatography method after solid phase extraction. RESULTS: One patient was withdrawn from the study because of poor compliance. Of the 14 patients who completed the study, nine did not meet the treatment response criterion of an improvement of >25% from the baseline total Y-BOCS score and a score of < or =3 for the global improvement item of the CGI (these patients were termed non-responders), while five did (responders). There were no differences in the main demographic and baseline clinical variables between responders and non-responders. Steady-state citalopram concentrations were similar in the two groups, suggesting that the anti-obsessional effects of citalopram were not related to pharmacokinetic differences between responders and non-responders. There was no linear relationship between steady-state citalopram concentrations and response. The citalopram concentrations and Y-BOCS scores of individual responders obtained at baseline and various study timepoints showed a sigmoid relationship when analysed using the E(max) (maximum change in Y-BOCS score) model, with a mean EC(50) value (drug concentration that elicits 50% of the E(max)) of 152 microg/L, whereas a similar analysis of the non-responders generated a flat line. CONCLUSION: The results of this preliminary study suggest that plasma citalopram concentrations may be related to the clinical response in responders, but do not seem to account for the lack of clinical effect in non-responders. These data, as well as the usefulness of the model in relating plasma concentrations to response, even after repeated administration, need to be validated by further investigations.

Pharmacokinetics and distribution of sodium 3,4-diaminonaphthalene-1-sulfonate, a Congo Red derivative active in inhibiting PrP(res) replication.

Sodium 3,4-diaminonaphthalene-1-sulfonate (CRA) is a compound, synthesised by our group from Congo Red (CR), that is active in preventing the pathological conversion of normal prion protein (PrP). As the precise mechanisms controlling the ways in which prions are distributed and infect the brain and other organs are not fully understood, studying the pharmacokinetics of drugs that are active against prions may clarify their targets and their means of inhibiting prion infection. This paper describes the pharmacokinetics of CRA in plasma, spleen and brain after single or repeated intraperitoneal or subcutaneous administration, as determined by means of specific and sensitive fluorimetric HPLC. A single intraperitoneal administration led to peak plasma CRA concentrations after 15 min, followed by biphasic decay with an apparent half-life of 4.3 h. After subcutaneous administration, T(max) was reached after 30 min, and was followed by a similar process of decay: Cmax and the AUC0-last were 25% those recorded after intraperitoneal administration. The mean peak concentrations and AUCs of CRA after a single intraperitoneal or subcutaneous administration in peripheral tissue (spleen) were similar to those observed in blood, whereas brain concentrations were about 2% those in plasma. After repeated intraperitoneal or subcutaneous doses, the Cmax values in plasma, brain and spleen were similar to those observed at the same times after a single dose. After repeated intraperitoneal doses, CRA was also found in the ventricular cerebrospinal fluid at concentrations of 1.8 +/- 0.2 microg(-1) mL, which is similar to, or slightly higher than, those found in brain. Brain concentrations may be sufficient to explain the activity of CRA on PrP reproduction in the CNS. However, peripheral involvement cannot be excluded because the effects of CRA are more pronounced after intraperitoneal than after intracerebral infection.

Neurochemical and behavioural modifications induced by scrapie infection in golden hamsters.

Scrapie-infected hamsters were tested for spontaneous motor activity and passive avoidance at various times after infection. After testing, some animals were killed and their whole brains assayed for norepinephrine, dopamine, serotonin and their metabolites. The apparent rate of turnover was estimated in terms of metabolite/amine concentrations. After 70 days, there was a decrease in passive avoidance and dopamine and serotonin. Passive avoidance correlated with the apparent rate of turnover of dopamine, whereas motor activity correlated with that of serotonin and dopamine.

Determination of sodium 3,4-diaminonaphthalene-1-sulfonate, a Congo Red derivative, in plasma and brain of hamsters by high-performance liquid chromatography after solid-phase extraction and ultraviolet absorbance.

In the search for compounds with similar or greater activity than Congo Red (CR) in protecting normal prion protein from being converted into the pathological form, we have synthesized various compounds which derive from CR. One of these is the sodium 3,4-diaminonaphthalene-1-sulfonate (RCA) which has an activity similar to CR in preliminary experiments. This study describes a method to determine RCA in plasma and in brain tissue by high-performance liquid chromatography (HPLC), using a solid-phase extraction and UV detection. RCA is an amphoteric molecule difficult to separate from biological matrices. Extraction was achieved by solid-phase extraction (ENV+ columns) together with the use of a counter ion. The resulting solid-phase extraction is efficient and rapid. RCA was separated on a Symmetry C18 250 x 4.6 mm I.D. 5 lm column at 1 ml/min using a 50 mM NaSO4 in 5 mM tetra-n-butylammoniumiodide (TEBA) in water-methanol (82:18, v/v) mobile phase. Retention times of RCA and I.S. were 21 and 24 min. The UV detector was set at 210 nm. The limit of quantitation was 0.5 microg/ml. The method has intra-assay and inter-assay accuracies higher than 95%, coefficients of variation ranging between 2.8 and 8.6%, and recovery rates between 74.3 and 80.1% in plasma and in brain tissue. A linear response to quantities of RCA from 0.5 to 100 microg/ml or 10 microg/g in plasma or brain was obtained. The present method allows the study of the pharmacokinetics of RCA in plasma after i.p. administration, and the distribution of the compound into the brain at the peak time.

Phagocytosis and killing of Candida albicans of polymorphonuclear cells in patients with organ transplant of periodontal disease.

BACKGROUND: The easiest defence system carried out by the organism, the inflammatory response, happens with the support of phagocyting cells: the polymorphonuclear leukocytes (PMNL) or neutrophils are the most important cell line acting as the first defence of the organism against bacterial agents. Previous studies have shown a correlation between a reduction of the immune function and development of periodontal disease. Furthermore, it is well known that transplant patients show a variety of oral lesions as a consequence of their therapy, in particular to immunosuppressive drugs. The aim of this study is to evaluate the phagocytosis and killing functions of PMNL in transplant patients and in patients with periodontal disease in comparison with a group of healthy subjects. METHODS: PMNL, were isolated by spontaneous sedimentation from heparinized blood and centrifugation of plasma on density medium. Phagocytosis rate was expressed as the percentage of Candida albicans phagocyted after 20' incubation and phagocyting PMNLs. Intracellular killing was expressed as the percentage of yeast cells killed. RESULTS: We did not find a significant decrease of phagocytosis in transplant patients and patients with periodontal disease while these two groups of patients showed a decrease of PMNL killing activity in respect to healthy controls, an effect which was unrelated to the severity of periodontal disease. CONCLUSIONS: These results suggest that a reduction of killing activity, either spontaneous or drug-induced, would contribute to the development of periodontal disease.

Adaptation to oxidative stress: effects of vinclozolin and iprodione on the HepG2 cell line.

It is well known that the dicarboximide fungicides, vinclozolin and iprodione, induce lipid peroxidation by means of oxygen activation in fungi, but their action on mammalian cells is not yet clear. We therefore investigated the effect of 1- and 24-h treatments with vinclozolin at concentrations of 25, 50, 100 microg/ml and iprodione at concentration of 62.5, 125, 250 microg/ml on malonaldehyde and free radical production and on reduced glutathione levels in the human HepG2 hepatoma cell line. The concentrations were chosen on the basis of neutral red cytotoxicity assays. One-hour treatment with the different concentrations of either vinclozolin or iprodione increased both malonaldehyde and free radical content, and decreased reduced glutathione levels, whereas 24-h treatment decreased malonaldehyde content and free radical production, and increased reduced glutathione concentration. These results suggest that the mammalian cells respond to the initial oxidative damage caused by the two dicarboximide fungicides by means of a characteristic adaptative phenomenon within 24 h. This hypothesis is supported by the antagonized effects caused by treatment with the two dicarboximide fungicides and buthionine sulfoximine 0.5 mM, a specific and irreversible inhibitor of reduced glutathione synthesis. The data confirm that the two dicarboximide fungicides maintain their specific action in mammalian cells, although this action is masked by adaptation.

Estudio de la compliance dínámica y la resistencia de la vía aérea en lactantes con neumonitis grave / Assessment of dynamic compliance and resistance of the airway in infants with severe pneumonitis

Existe muy poca información respecto de las alteraciones de la mecánica respiratoria en lactantes con neumonitis grave. Por esa razón se estudiaron la compliance dinámica (CD) y la resistencia de la vía área (R) en 8 lactantes con neumonitis en ARM, menores de dos meses, a fin de conocer mejor los cambios de la dinámica respiratoria en esa condición. Las mediciones de la CD y la R se efectuaron en condiciones controladas de estudio en tres períodos: a- priemer día de ARM; b- días ulteriores y c. previo a la exturbación. Se observó una disminución de la CD (0.64 más menos 0.32 ml/cm H20/kg) y aumento de la R (193.6 más menos 113.1 cm H2O/L/S) en el primer día de ARM con mejoria de los días ulteriores y una tendencia a la normalización de los valores medios preextubación: CD (1.13 más menos o.26 ml/cm H20/Kg) y R (45.5 más menos 27.2 cm H2O/L/S). El importante aumento de la R podría ser la alteración funcional respiratoria más importante en lactantes con neumonitis grave ARM y la medición de esta viariable en unión con los datos clínicos podría contribuir al diagnóstico y la terapéutica de esta patología.

Carbendazim and n-butylisocyanate: metabolites responsible for benomyl double action on cytochrome P450 in HepG2 cells.

Changes in the cytochrome P450 monooxygenase system were investigated in HepG2 cells treated for 24 h with 1.25, 2.5, 5, 10 and 20 microg/ml of carbendazim (MBC) and n-butylisocyanate (BIC), the principal benomyl metabolites. The results show that n-butylisocyanate leads to a decrease in both ethoxyresorufin deethylase (P4501A1) (EROD) and ethoxycoumarin deethylase (P4502B) (ECOD), whereas MBC has no effect on EROD and increases ECOD. The decrease in ECOD and EROD activities after BIC treatment can be attributed to the detrimental action of this substance. The MBC-induced increase in ethoxycoumarin can be considered an enzyme-specific inductive phenomenon. This hypothesis was confirmed by Western immunoblot analysis and treatment with actinomycin D 8 x 10(-4) microM: the first showed an increase in P4502B isoenzyme content and the second evidence of a partial block of the increase in ECOD activity induced by MBC. Given these results, MBC and BIC seem to be the metabolites responsible for the double opposite action of their parent compound benomyl. Data deriving from an equimolar mixture of the two metabolites suggest that benomyl activity on some cytochrome P450 isoenzymes is the result of a balance between the action of the single metabolites (Radice et al., 1996).

Carbon dioxide digital subtraction angiography in oncological-interventional radiology.

AIMS AND BACKGROUND: The aim of this work is to demonstrate the usefulness of carbon dioxide, used as contrast agent, in special indications in vascular interventional oncological procedures. METHODS: We studied 40 patients with digital subtraction angiography enhanced with CO2 as a contrast agent. At the same time we utilized also, in all cases, jodinated contrast agent to evaluate the different opacification gradient, the different viscosity range and the different perfusion. RESULTS: The low viscosity of CO2 allows demonstration of the presence of even minimal blood losses in gastrointestinal tumors and enhances arteriovenous shunts in hepatocellular carcinoma. Carbon dioxide can also be employed to assess the patency of small-sized catheters for chemotherapy infusion which do not allow easy injection of the traditional iodinated contrast agents characterized by high viscosity. CONCLUSION: Carboangiographic study combined to digital subtraction angiography can clear some diagnostic problems and is further method to assess the outcome of angiographic interventional procedures in oncology.

Cytotoxic activity and mechanism of action of 5-Aza-2'-deoxycytidine in human CML cells.

We investigated the cytotoxic activity and some aspects of the mode of action of 5-aza-2'-deoxycytidine (Aza-dC) in 21 primary cultures of leukemic cells freshly obtained from patients with chronic myeloid leukemia (CML) in blast crisis. The cytotoxic potency of Aza-dC was comparable or even greater than that of 1-beta-D-arabinofuranosylcytosine (Ara-C) in most cases, suggesting that this drug has potential in the therapy of blast crisis of CML. Drug incorporation into DNA was evaluated by exposing leukemic cells simultaneously to 3H-Aza-dC at the concentration of 0.1 micrograms/ml and 14C-thymidine (TdR) used as internal standard. Incorporation of Aza-dC into DNA was detectable in all cases. In 17 samples we evaluated the DNA integrity of leukemic cells exposed to Aza-dC using alkaline elution techniques. The drug caused a detectable amount of DNA alkali labile sites (ALS). DNA-ALS increased in cells exposed to Aza-dC concentrations from 0.1 to 1 microgram/ml but did not further increase at 10 micrograms/ml. A plateau in the levels of DNA-ALS was also seen in human K562 cells exposed to increasing concentrations of Aza-dC from 5 to 10 micrograms/ml, whereas in these cells Aza-dC incorporation into DNA increased with increasing Aza-dC concentrations. Therefore, DNA-ALS caused by Aza-dC are not simply the result of the chemical decomposition of azacytosine molecules incorporated into DNA, but are presumably the result of a saturable DNA repair mechanism (e.g., glycosylases) leading to formation of the apyrimidinic sites.

Infection and antibiotic therapy in 4000 burned patients treated in Milan, Italy, between 1976 and 1988.

The pathogenic flora, isolated from burn wounds of patients admitted to a burn care unit during the years between 1976 and 1988 were typed and the in vitro susceptibility to antibacterial agents was recorded. Between 1976 and 1988 the general therapeutic approach was changed three times, in congruence with the prevalent nosocomial bacterial resistance. The most frequent isolates were: Pseud. aeruginosa, Staphylococcus aureus, Enterococcus spp., Proteus mirabilis, Escherichia coli, Enterobacter cloacae, Klebsiella spp. and other Enterobacteriaceae, such as Acinetobacter, Citrobacter. The most striking finding was the increase in antibiotic-resistant Enterococcus isolates. Staph. aureus, Klebsiella and E. cloacae showed susceptibility to cephalosporins, imipenem, pefloxacin, vancomycin; Enterococcus susceptibility to pefloxacin and vancomycin, and Pseud. aeruginosa sensitivity to piperacillin, amikacin, tobramycin was generally good. E. coli showed a satisfactory susceptibility on average, and P. mirabilis showed a good sensitivity to piperacillin, cephalosporins, amikacin, tobramycin, aztreonam and imipenem. Thus, the general bacterial flora and susceptibility have remained mostly unchanged over the years, with the conspicuous exception of Enterococcus spp. and E. cloacae, which demonstrated a marked increase in incidence, with a concomitant dramatic decrease in the sensitivity of Enterococcus spp. to antibiotics.

Primary pharmaco-toxicological evaluation of 2-iodomelatonin, a potent melatonin agonist.

Series of experiments aimed at a primary pharmaco-toxicological evaluation of 2-iodomelatonin, a high-affinity melatonin analogue, were performed. In the rat ovulation-inhibition model, 2-iodomelatonin was much more potent than either melatonin or 6-chloromelatonin. The acute toxicity was extremely low and close to, though slightly higher than that reported previously for melatonin. In the rat, 2-iodomelatonin was slowly metabolized in vivo; its apparent elimination half-life was about 60 minutes, much longer than that reported for melatonin. The in vitro mutagenesis tests demonstrated clearly that 2-iodomelatonin in concentrations, exceeding the dose range employed in the in vivo studies, was actually devoid of mutagenic effects. The obtained results suggest that 2-iodomelatonin deserves a detailed pharmaco-toxicological evaluation and could be eventually used in pharmacokinetic and pharmacodynamic studies in humans.

Studies of the differentiation properties of camptothecin in the human leukaemic cells K562.

Camptothecin, a specific inhibitor of topoisomerase I, caused erythroid differentiation of the human leukaemia cell-line K562, as assessed by benzidine staining at 70 h recovery following a 60 min treatment of the cells. Differentiation was confirmed by increased levels of epsilon-globin and gamma-globin mRNA in the treated cells and was accompanied by down-regulation of c-myb mRNA. Synchronisation of K562 cells by non-cytotoxic doses of methotrexate increased the differentiation induced by camptothecin, without affecting the camptothecin-induced inhibition of cellular proliferation. Camptothecin induction of differentiation and inhibition of proliferation may occur by independent mechanisms.