Intra-arterial chemotherapy for retinoblastoma treatment in Chile: Experience and results 2013-2020.

OBJECTIVE: To establish the success rate of salvage intra-arterial chemotherapy (IAC), defined as the percentage of eyes that achieved tumoral remission and avoided enucleation. The second objective was the clinical characterization, catheterization results, and associated local and systemic complications. METHODS: Retrospective, interventional case series of 29 patients (35 eyes) with persistent or recurrent retinoblastoma. RESULTS: A total of 73 salvage IAC procedures with topotecan and melphalan were carried out. Success rate was 77% at a mean follow-up of 41.4 months. All patients with only one remaining eye avoided enucleation (10 cases). Catheterization was successful in 98.6% of cases. The types of catheterizations were as follows: 71.2% supraselective ophthalmic artery, 12.3% occlusion pump assisted supraselective ophthalmic artery, 16.4% selective external carotid with retrograde flow. 14% of patients suffered local adverse effects: 1 (2.8%) transitory ptosis, 1 (2.8%) transitory oculomotor nerve palsy, 2 (5.7%) aseptic cellulitis and 1 (2.8%) periorbitary pigmentation. 4.1% (3 cases) suffered neutropenia due to medullar chemosuppression. There were no cases of severe anemia or thrombocytopenia. There were no cerebral ischemic events or mortality associated to the procedure. CONCLUSION: IAC with melphalan and topotecan is a safe and effective treatment option for persistent or recurrent retinoblastoma, able to reduce enucleation rates.

Quimioterapia intraarterial para el tratamiento del retinoblastoma en Chile: experiencia y resultados, período 2013-2020 / Intra-arterial chemotherapy for retinoblastoma treatment in Chile: experience and results 2013-2020

Objetivo Establecer la tasa de éxito de la quimioterapia intraarterial (QIA) en modalidad de rescate expresada en el porcentaje de ojos que lograron remisión tumoral y evitaron la enucleación. El segundo objetivo fue analizar la caracterización clínica, resultados del cateterismo, complicaciones locales y sistémicas asociadas. Métodos Estudio retrospectivo de serie de casos intervencional de 29 pacientes (35 ojos) con retinoblastoma intraocular persistente o recidivado. Resultados Se realizaron un total de 73 procedimientos de QIA con topotecán y melfalán en modalidad de rescate. La tasa de éxito de la QIA fue del 77% en un seguimiento promedio de 41,4 meses. Todos los casos con ojo único evitaron la enucleación de su ojo residual (10 casos). El cateterismo fue exitoso en un 98,6%. Los tipos de cateterización logrados fueron los siguientes: supraselectiva por arteria oftálmica (71,2%), supraselectiva por arteria oftálmica asistida con balón de oclusión en carótida externa (12,3%), selectiva por rama de carótida externa con flujo retrógrado (16,4%). Se reportaron efectos adversos locales en el 14% de los pacientes: una (2,8%) ptosis palpebral transitoria, una (2,8%) parálisis del sexto par transitoria, 2 (5,7%) celulitis aséptica y una (2,8%) pigmentación de región periorbitaria. La frecuencia de neutropenia por quimiosupresión medular fue del 4,1% (3 casos). No hubo casos de anemia ni trombocitopenia severas. No hubo eventos isquémicos cerebrales ni mortalidad asociada al procedimiento. Conclusión La QIA con melfalán y topotecán es una alternativa segura y efectiva para el tratamiento del retinoblastoma persistente o recidivado, permitiendo reducir las tasas de enucleación (AU)

Objective To establish the success rate of salvage intra-arterial chemotherapy (IAC), defined as the percentage of eyes that achieved tumoral remission and avoided enucleation. The second objective was the clinical characterization, catheterization results, and associated local and systemic complications. Methods Retrospective, interventional case series of 29 patients (35 eyes) with persistent or recurrent retinoblastoma. Results A total of 73 salvage IAC procedures with topotecan and melphalan were carried out. Success rate was 77% at a mean follow-up of 41.4 months. All patients with only one remaining eye avoided enucleation (10 cases). Catheterization was successful in 98.6% of cases. The types of catheterizations were as follows: 71.2% supraselective ophthalmic artery, 12.3% occlusion pump assisted supraselective ophthalmic artery, 16.4% selective external carotid with retrograde flow. 14% of patients suffered local adverse effects: 1 (2.8%) transitory ptosis, 1 (2.8%) transitory oculomotor nerve palsy, 2 (5.7%) aseptic cellulitis and 1 (2.8%) periorbitary pigmentation. 4.1% (3 cases) suffered neutropenia due to medullar chemosuppression. There were no cases of severe anemia or thrombocytopenia. There were no cerebral ischemic events or mortality associated to the procedure. Conclusion IAC with melphalan and topotecan is a safe and effective treatment option for persistent or recurrent retinoblastoma, able to reduce enucleation rates (AU)

An international survey in Latin America on the practice of interventional cardiology during the COVID-19 pandemic, with a particular focus on myocardial infarction.

INTRODUCTION: A reduction in the number of interventional cardiology procedures has emerged as a result of the COVID-19 pandemic. A survey was performed to quantify this decrease and the impact on the management of myocardial infarction in Latin America. METHODS: A telematic survey was conducted for all countries in Latin America. Diagnostic catheterisations, coronary and structural interventions, as well as the incidence and delay to reperfusion therapy of myocardial infarction (STEMI), were recorded. Two periods were compared: from 24 February to 8 March 2020 (pre-COVID-19) and another 2­week period that varied according to country (COVID-19). RESULTS: Responses were obtained from 79 centres in 20 countries. There was a significant decrease in the number of diagnostic procedures (-65.2%), coronary interventions (-59.4%), structural therapeutics (-86.1%) and STEMI care (-51.2%). A decrease was noted in the incidence of STEMI, but also a delay in the time to STEMI reperfusion. While there was a variation in activity in interventional cardiology between countries, patient behaviour was rather homogeneous. CONCLUSIONS: A significant reduction in healthcare activity has been noted during the COVID-19 pandemic, including STEMI care, with the risk of increased mortality and/or morbidity following STEMI. Healthcare providers should encourage patients with suspected symptoms of STEMI to call for emergency care to ensure rapid diagnosis and timely reperfusion treatment.

Forma de presentación "prono-doloroso-like" del síndrome de Parsonage-Turner / Parsonage-Turne síndrome "pulled elbow-like" presentation form

Introducción: El síndrome de Parsonage-Turner es una neuritis del plexo braquial de etiología desconocida. Se ha des-crito su aparición tras procesos infecciosos, por lo que se sospecha un mecanismo autoinmune. Su descripción en la edad pediátrica se limita a casos aislados. En los adultos, la sintomatología típica es un dolor súbito e intenso, localizado en el hombro y la región proximal de la extremidad superior, seguido de parálisis flácida y amiotrofia. Caso clínico: Lactante de 14 meses de edad que consulta por presentar una impotencia funcional de los miembros superiores de 48 horas de evolución. Los días previos mostró una infección respiratoria de las vías altas. Presentaba el brazo derecho en posición de prono, debilidad de la musculatura proximal de ambas extremidades superiores, sobre todo la derecha, e incapacidad para la movilización. Se detectó rhinovirus en la reacción en cadena de la polimerasa de moco nasal. El electromiogra-ma (EMG) del deltoides demostró una denervación aguda intensa de los músculos proximales de ambas extremidades superiores, sobre todo la derecha, compatible con una plexitis braquial bilateral. Conclusiones: El espectro clínico de presentación de la neuralgia amiotrófica puede ser distinto en la edad pediátrica. El dolor, característico de la forma adulta, puede no estar presente. Su forma de presentación puede asemejarse a un prono doloroso, por lo que deberemos incluirlo en su diagnóstico diferencial. El diagnóstico se basa en hallazgos clínicos; son de utilidad la resonancia magnética y el EMG, que debe realizarse 2-3 semanas tras el inicio del cuadro. El conocimiento de esta entidad permite establecer un diagnóstico precoz, lo que evita tratamientos potencialmente yatrogénicos, y anticipar el pronóstico

Introduction: Parsonage-Turner syndrome is a brachial plexus neuritis of unknow etiology. An autoinmune mecha-nism is suspected because of its appearance after infections. It predominantly affects proximal muscles of upper ex-tremities, with a first painful phase, which evolves to paresis and atrophy of the affected muscles. His description in pediatric patients is limited to isolated cases. Case report: 14 months infant consulting for weakness of upper limbs. He had an upper respiratory tract infection the previous days. Examination revealed weakness of the proximal muscles of the both arms, more marked on the right side and inability to active mobility simulating a pulled elbow. Magnetic resonance imaging of neck and shoulder showed no structural pathology. The electromyogram performed at 3 weeks of the onset of symptoms demonstrated acute denervation of the proximal arm muscles compatible with bilateral brachial plexitis. Rhinovirus was detected in polimerasa chain reaction in nasopharyngeal aspirate. Conclusions: Parsonage-Turner syndrome is an entity to consider in painful shoulder or upper limb functional impo-tence, as pulled elbow. Diagnosis is based on clinical findings. It's useful to rule one MRI and EMG (which must be per-formed 2-3 weeks after onset). It has spontaneous evolution partially favorable to rehabilitation and anti-inflammatory treatment. Knowledge of this entity allows proper handling, avoiding iatrogenic treatments, and allows anticipate the outcome

Tolerance to deer herbivory and resistance to insect herbivores in the common evening primrose (Oenothera biennis).

The evolution of plant defence in response to herbivory will depend on the fitness effects of damage, availability of genetic variation and potential ecological and genetic constraints on defence. Here, we examine the potential for evolution of tolerance to deer herbivory in Oenothera biennis while simultaneously considering resistance to natural insect herbivores. We examined (i) the effects of deer damage on fitness, (ii) the presence of genetic variation in tolerance and resistance, (iii) selection on tolerance, (iv) genetic correlations with resistance that could constrain evolution of tolerance and (v) plant traits that might predict defence. In a field experiment, we simulated deer damage occurring early and late in the season, recorded arthropod abundances, flowering phenology and measured growth rate and lifetime reproduction. Our study showed that deer herbivory has a negative effect on fitness, with effects being more pronounced for late-season damage. Selection acted to increase tolerance to deer damage, yet there was low and nonsignificant genetic variation in this trait. In contrast, there was substantial genetic variation in resistance to insect herbivores. Resistance was genetically uncorrelated with tolerance, whereas positive genetic correlations in resistance to insect herbivores suggest there exists diffuse selection on resistance traits. In addition, growth rate and flowering time did not predict variation in tolerance, but flowering phenology was genetically correlated with resistance. Our results suggest that deer damage has the potential to exert selection because browsing reduces plant fitness, but limited standing genetic variation in tolerance is expected to constrain adaptive evolution in O. biennis.

La importancia de ser cuidadosos con los conceptos en los trastornos del espectro autista / The importance of being careful with the concepts on autism spectrum disorders

No disponible

Tratamiento farmacológico no estimulante en el trastorno por déficit de atención e hiperactividad (TDAH) / Non-stimulant drug treatment in attention déficit hyperactivity disorder (ADHD)

La elección del fármaco adecuado en el tratamiento del trastorno por déficit de atención e hiperactividad (TDAH) debe basarse en la característica individuales del paciente. El tamaño de efecto de los fármacos no estimulantes es menor que el de los estimulantes, pero esta diferencia se minimiza en estudios de larga duración y en pacientes naïve. Se debe considerar su uso en el caso de comorbilidades como el trastorno por tics, el trastorno ansioso depresivo o en el abuso de sustancias. Dentro del grupo de fármacos no estimulantes, la atomoxetiva en el único aprobado en España para esta indicación, con un inicio de acción que puede tardar varias semanas. Su mecanismo de acción se basa en el bloqueo de la recaptación de noradrenalida. La clonidina, el bupropión y los antidepresivos tricíclicos están disponibles par su uso pero no cuentan con indicación para el TDAH. Próximamente contaremos con nuevos recursos terapéuticos en este grupo, con la aprobación de uso de la guanfacina de liberación prolongada (AU)

Choosing the right drug in the treatment of ADHD should be based on individual patient characteristics. The effect size of the non-stimulant drug is less than the stimulant, but this difference is minimized in long-term studies or in naive patients. Its use should be considered in the case of comorbidities such as tic disorder, depressive anxiety disorder or substance abuse. Within the group of non-stimulant drugs, atomoxetine is the only approved for this indication in Spain, with its onset of action may take several weeks. Its mechanism of action in based on blocking the reuptake of norepinephrine. Clonidine, bupropion and tricyclic antidepressants are available for use but not indicated for ADHD. Coming soon will have new therapeutic resources in this group, with the approval of use of guanfacine extended release (AU)

Síndrome de Horner contralateral asociado a bloqueo de ganglio estrellado: reporte de caso y revisión de la literatura / Contralateral Horner's syndrome associated with stellate ganglion block: case report and literature review

Se describe un caso de síndrome de Horner contralateral luego de bloqueo de ganglio estrellado. Se trata de un varón de 56 años con diagnóstico de síndrome doloroso regional complejo tipo II en miembro superior derecho quien posterior a la aplicación de anestésico local guiado por ecografía en proximidad al ganglio estrellado derecho presenta síndrome de Horner izquierdo. El síndrome de Horner contralateral a un bloqueo de ganglio estrellado es una entidad de ocurrencia supremamente rara, en nuestra práctica se presentó uno de los pocos casos reportados en la literatura, de interés para la comunidad científica (AU)

We describe a case of contralateral Horner’s syndrome following stellate ganglion block. A 56 years old man diagnosed with complex regional pain syndrome type II in right upper arm, who developed after the application of local anesthetic guided by ultrasound in proximity to the right stellate ganglion presented left Horner’s syndrome. The contralateral Horner’s syndrome following stellate ganglion block is a rare entity. In our practice occurred one of the few cases reported in the literature, which is of great interest for the medical community (AU)

Supraglotitis atípica en la era postepiglotitis / Atypical supraglottitis in postepiglottitis era

No disponible

Enfermedad de Kikuchi-Fujimoto en una portadora del VIH / Kikuchi-Fujimoto disease in an HIV carrier

No disponible

Different effects of unexpected changes in environmental conditions on prepulse inhibition in rats and humans.

The reduction of the startle response to an auditory stimulus caused by the presentation of another stimulus of lower intensity closely preceding it, a phenomenon known as prepulse inhibition (PPI), can be modulated by changes in dopaminergic activity. Schmajuk, Larrauri, De la Casa, and Levin (2009) demonstrated that this dopaminergic modulation of PPI in rats can be influenced by manipulating the experimental context, specifically by introducing changes in the ambient lighting condition that include novel elements. In this paper we analyze the effects of introducing changes in context illumination on PPI in male rats (Experiment 1) and humans (Experiment 2). The results with rats showed a reduction of PPI when the illumination condition switched from dark to light, but not from light to dark. In the experiment with human participants the reduction of PPI occurred for both changes in illumination conditions. The animal experiment results are interpreted in terms of competing exploratory behavior that appear when the context is illuminated after the dark-light transition; while in the case of human participants a perceptual and/or attentional mechanism after both illumination transitions is proposed, which may result in a reduced processing of the prepulse and subsequent lower PPI.

Synthetic peptides from Plasmodium falciparum apical membrane antigen 1 (AMA-1) specifically interacting with human hepatocytes.

Plasmodium falciparum apical membrane antigen 1 (AMA-1) is expressed during both the sporozoite and merozoite stage of the parasite's life cycle. The role placed by AMA-1 during sporozoite invasion of hepatocytes has not been made sufficiently clear to date. Identifying the sequences involved in binding to hepatocytes is an important step towards understanding the structural basis for sporozoite-hepatocyte interaction. Binding assays between P. falciparum AMA-1 peptides and HepG2 cell were performed in this study to identify possible AMA-1 functional regions. Four AMA-1 high activity binding peptides (HABPs) bound specifically to hepatocytes: 4310 ((74)QHAYPIDHEGAEPAPQEQNL(93)), 4316 ((194)TLDEMRHFYKDNKYVKNLDE(213)), 4321 ((294)VVDNWEKVCPRKNLQNAKFGY(313)) and 4332 ((514)AEVTSNNEVVVKEEYKDEYA(533)). Their binding to these cells became saturable and resistant to treatment with neuraminidase. Most of these peptides were located in AMA-1 domains I and III, these being target regions for protective antibody responses. These peptides interacted with 36 and 58 kDa proteins on the erythrocyte surface. Some of the peptides were found in exposed regions of the AMA-1 protein, thereby facilitating their interaction with host cells. It is thus probable that AMA-1 regions defined by the four peptides mentioned above are involved in sporozoite-hepatocyte interaction.

Plasmodium falciparum EBA-140 kDa protein peptides that bind to human red blood cells.

The erythrocyte-binding antigen 140 (EBA140) sequence was chemically synthesized in 61 20-mer sequential peptides covering the entire 3D7 protein strain, each of which was tested in erythrocyte-binding assays. Peptides 26135, 26144, 26147, 26160, 26170 and 26177 presented high erythrocyte-binding activity, with affinity constants ranging from 350 to 750 nM. Critical erythrocyte-binding residues were determined by competition-binding assays with glycine analogous peptides. Cross-linking assays with SDS-PAGE from high erythrocyte membrane protein binding peptides showed that all these peptides bound specifically to 25, 52 and 75 kDa erythrocyte membrane proteins. The nature of these receptor sites was studied in peptide-binding assays using enzyme-treated erythrocytes, showing that these protein receptors are susceptible to structural changes provoked by enzyme treatment (neuraminidase, trypsin or chymotrypsin). Inhibition invasion assays in 'in vitro' cultures showed that all specific high binding sequences were able to inhibit invasion by 11-69% at 200 microM concentration.

Plasmodium falciparum: binding studies of peptide derived from the sporozoite surface protein 2 to Hep G2 cells.

Plasmodium falciparum sporozoite surface protein 2 (Pf SSP2), also called thrombospondin related anonymous protein (TRAP), is involved in the process of sporozoite invasion of hepatocytes. Pf SSP2/TRAP possesses two different adhesion domains sharing sequences and structural homology with von Willebrand factor A-domains and human repeat I thrombospondin (TSP). Pf SSP2/TRAP has also been implicated in sporozoite mobility and in mosquito salivary gland invasion processes. We tested 15-mer long synthetic peptides having five overlapping residues covering the complete protein Pf SSP2 sequence in binding assays to Hep G2 cells. In these 57 peptides, 21 high-activity binding peptides (HABPs) were identified; five were in the adhesion domains already described and 16 were in two regions toward the protein's carboxy and middle terminal part. Six HABPs showed conserved amino acid sequences: 3243 (21FLVNGRDVQNNIVDE35), 3279 (201FLVGCHPSDGKCNLY215), 3287 (241TASCGVWDEWSPCSV255), 3289 (251SPCSVTCGKGTRSRK265), 3327 (441ERKQSDPQSQDNNGNY455) and 3329 (451DNNGNRHVPNSEDREY465). The HABPs show saturable binding and dissociation constants between 140 and 900 nm with 40 000-855 000 binding sites per cell. The 3279 (201FLVGCHPSDGKCNLY215), 3323 (421NDKSDRYIPYSPLSP435) and 3331 (461SEDRETRPHGRNNENY475) HABPs have B epitopes in their sequences; these have previously been recognized by antibodies partially inhibiting hepatocyte invasion and development of the hepatic state. The 3287 (241TASCGVWDEWSPCSV255) and 3289 (251SPCSVTCGKGTRSRK265) HABPs share common sequences with the Pf SSP2/TRAP region II plus, which is present in a great number of adhesion proteins. Based on this information, six new peptides covering the high binding regions identified previously were synthesized and, using a competition assay, the amino acid involved in the binding were determined.

Plasmodium falciparum circumsporozoite (CS) protein peptides specifically bind to HepG2 cells.

Hepatocyte invasion by malaria parasites is mediated by specific molecular interactions. Several lines of evidence suggest the importance of the surface plasmodial circumsporozoite (CS) protein in the sporozoite invasion of hepatocytes. Identification of the sequences involved in binding to hepatocytes is an important step towards understanding the structural basis for the sporozoite-hepatocyte interaction. In this study, binding assays between Plasmodium falciparum CS peptides and HepG2 cells were performed. Fifteen overlapping residue 20 mer long peptides, spanning the entire CS sequence, were tested in HepG2 cell binding assays. Five High Binding Activity Peptides (HBAPs) to HepG2 cells were identified: 4593, (NANPNANPNANP); 4383, (NSRSLGENDDGNNEDNEKLR); 4388, (GNGQGHNMPNDPNRNVDENA); 4389, (HNMPNDPNRNVDENANANSA) and 4390, (DPNRNVDENANANSAVKNNN). The HBAP HepG2 interaction is independent of charge and amino-acid composition, but sequence dependent. Four HBAPs (4383, 4388, 4389 and 4390) are bound with similar affinity to a 50 kDa molecule. These HBAPs define three Hepatocyte Binding Sequences (HBSs): HBS-1, located between residues 68 and 87 (HBAP 4383); HBS-11, the repeat NANP region (HBAP 4593), for which anti repeat antibodies are able to specifically inhibit sporozoite invasion of hepatocytes have been reported; and HBS-111, between residues 286 and 315 (HBAPs 4388, 4388 and 4390), respectively. Interestingly, HBS 111 carries two earlier-reported B-epitopes (underlined) in peptides 4388, 4389 and 4390 (GNGQGHNMPNDPNRNVD ENANANSAVKNN) in its sequence. The HBSs reported here show lesser interspecie-variability than the entire protein in species invading the same kind of hepatic cells. This data supports these HBSs' important role in CS-protein function; they could be used as ligand by the sporozoite to invade hepatic cells.

Plasmodium falciparum acid basic repeat antigen (ABRA) peptides: erythrocyte binding and biological activity.

Non overlapping 20-mer peptides, covering the complete sequence of acid basic repeat antigen (ABRA) of Plasmodium falciparum, were synthesised and tested in binding assays to erythrocytes. Five peptides localised in the N-terminal region coded 2148 (121LQSHKKLIKALKKNIESYQN(140)), 2149 (141KKHLIYKNKSYNPLLLSCVK(160)), 2150 (161KMNMLKENVDYIQKNQNLFK(180)), 2152 (201YKSQGHKKETSQNQNENNDN(220)) and 2153 (221QKYQEVNDEDDVNDEEDTND(240)) specifically bind to erythrocytes. These peptides bind independently of the peptide and erythrocyte charge, with high affinity (Kd between 70 and 180 nM) and the hydrophobic interaction is important for this binding ( approximately 30% hydrophobic critical residues). These results allow us define a specific erythrocyte binding region (residues 121-240), which may bound to at least three different binding sites on erythrocytes. Peptide 2153 shares the underlined sequence 221QKYQEVNDEDDVNDEEDTND(240) with an earlier 18-mer peptide recognised by human exposed sera. Peptides number 2148 and 2149 in vitro inhibit erythrocyte invasion by merozoites. We found that 2149 peptide and some of its glycine analogues show specific haemolytic and/or antimicrobial activity. We discuss a possible role of ABRA or its regions in the merozoite invasion of erythrocyte.

Plasmodium falciparum AMA-1 erythrocyte binding peptides implicate AMA-1 as erythrocyte binding protein.

The role of AMA-1 during merozoite invasion has not yet been determined. However, reported experimental evidence suggests that this protein can be used, in particular as erythrocyte-binding protein, since, Fab fragments against this protein are able to block merozoite invasion. Using a previously described methodology, eight peptides with high binding activity to human erythrocyte, scattered along the different domains and having around 130 nM affinity constants, were identified in the Plasmodium falciparum AMA-1 protein. Their binding activity was sialic acid independent. Some of these peptides showed homology with the erythrocyte binding domains of one of the apical organelle protein family, MAEBL, identified in rodent malarial parasites. One of these peptides shares amino acid sequence with a previously reported B-cell epitope which induces antibodies to block parasite growth. The critical residues were identified for erythrocyte binding conserved peptides 4313 (DAEVAGTQYRLPSGKCPVFG), 4321 (VVDNWEKVCPRKNLQNAKFG), 4325 (MIKSAFLPTGAFKADRYKSH) and 4337 (WGEEKRASHTTPVLMEKPYY). All conserved peptides were able to block merozoite invasion of new RBC and development, suggesting that these peptides are involved in P. falciparum invasion.

Serine repeat antigen peptides which bind specifically to red blood cells.

It has been reported that serine repeat antigen (SERA) binds directly to human erythrocyte membranes, inside-out vesicles and intact mouse erythrocytes. Similarly, mAbs specific against SERA are effective in blocking red blood cell (RBC) invasion by P. falciparum merozoites. Furthermore, the N-terminal recombinant SERA fragment inhibits the merozoite invasion of erythrocyte. In this study of 49 non-overlapping 20-residue-long peptides encompassing the whole SERA protein FCR3 strain, seven peptides having high RBC binding activity were found. Six of these peptides (three from the SERA N-terminal domain) are located in conserved regions and show affinity constants between 150 and 1100 nM, Hill coefficients between 1.5 and 3.0 and 30000-120000 binding sites per cell. Some of these peptides inhibited in vitro merozoite invasion of erythrocyte and intra-erythrocytic development. Residues which are critical in the binding to erythrocytes (in bold face), i.e. 6725 (YLKETNNAISFESNSGSLEKK), 6733 (YALGSDIPEKCDTLASNCFLS), 6737 (YDNILVKMFKTNENNDKSELI), 6746 (DQGNCDTSWIFASKYHLETI), 6754 (YKKVQNLCGDDTADHAVNIVG) and 6762 (NEVSERVHVYHILKHIKDGK), were determined by means of competition assays with high-binding peptide glycine analogues. The identification of peptides which bind to erythrocyte membrane is important in understanding the process of RBC invasion by P. falciparum merozoites.