RESUMEN
Se presentan 3 casos de pacientes, con 66, 80 y 23años de edad, que presentaron una pérdida de visión unilateral. La tomografía de coherencia óptica (OCT) mostró edema macular junto con una lesión redondeada de pared hiperreflectiva y la angiografía con fluoresceína (AFG) de dos de ellos, dilataciones aneurismáticas perifoveales hiperfluorescentes con exudación. Ninguno de los casos mostró respuesta al tratamiento tras un año de seguimiento, diagnosticándose finalmente de complejo anómalo vascular exudativo perifoveal (PEVAC) (AU)
We present three cases of patients aged 66, 80 and 23, who presented unilateral vision loss. Optical coherence tomography (OCT) in all of them showed macular oedema and a rounded lesion with hyper-reflective wall, and fluorescein angiography (FAG) in two of them showed hyperfluorescent perifoveal aneurysmal dilations with exudation. None of the cases showed response to treatment after one year of follow-up, finally being diagnosed with perifoveal exudative vascular anomalous complex (PEVAC) (AU)
Asunto(s)
Humanos , Masculino , Femenino , Adulto Joven , Anciano , Anciano de 80 o más Años , Exudados y Transudados/diagnóstico por imagen , Edema Macular/diagnóstico por imagen , Malformaciones Vasculares/diagnóstico por imagen , Trastornos de la Visión/diagnóstico por imagen , Ceguera , Angiografía con Fluoresceína , Tomografía de Coherencia ÓpticaRESUMEN
We present three cases of patients aged 66, 80 and 23, who presented unilateral vision loss. Optical coherence tomography (OCT) in all of them showed macular oedema and a rounded lesion with hyperreflective wall, and fluorescein angiography (FAG) in two of them showed hyperfluorescent perifoveal aneurysmal dilations with exudation. None of the cases showed response to treatment after one year of follow-up, finally being diagnosed with Perifoveal Exudative Vascular Anomalous Complex (PEVAC).
Asunto(s)
Edema Macular , Malformaciones Vasculares , Humanos , Exudados y Transudados/diagnóstico por imagen , Angiografía con Fluoresceína/métodos , Trastornos de la VisiónAsunto(s)
Loiasis , Humanos , Animales , Loiasis/diagnóstico , Dietilcarbamazina , Ivermectina , LoaRESUMEN
RESEARCH QUESTION: Is the DuoStim strategy an effective alternative to two conventional ovarian stimulation cycles in poor-prognosis patients undergoing preimplantation genetic testing for aneuploidies (PGT-A) to improve euploidy rates and obtain the first euploid embryo in less time? DESIGN: This randomized controlled trial was performed at IVI Madrid between June 2017 and December 2020 and included 80 patients with a suboptimal profile aged 38 or older undergoing PGT-A cycles. Patients were blindly randomized into two groups: 39 women underwent two ovarian stimulations in consecutive cycles (control group), whereas the double stimulation strategy was applied to 41 women (DuoStim group). The main outcome was the euploidy rate in each group. The secondary outcomes were the time it took to obtain a euploid embryo and the main cycle outcomes. RESULTS: The baseline characteristics of the patients were similar. No differences were found between the control group and the DuoStim group in the mean days of stimulation (21.3 ± 1.6 versus 23.0 ± 1.4, Pâ¯=â¯0.10), total gonadotrophins (4005 ± 450 versus 4245 ± 430, Pâ¯=â¯0.43), metaphase II oocytes (8.7 ± 1.8 versus 6.8 ± 1.7, Pâ¯=â¯0.15) or euploid embryos obtained (0.8 ± 0.4 versus 0.6 ± 0.4, Pâ¯=â¯0.45). The euploid rate per randomized patient (ITT) was 16.1% in the control group versus 22.7% in the DuoStim group, with P-values of 0.371, and the euploidy rate per patient treated was 39.0% versus 45.7% in the control versus DuoStim groups. However, there was a significant difference in the average number of days it took to obtain a euploid blastocyst, favouring the DuoStim group (44.1 ± 2.0 versus 23.3 ± 2.8, P < 0.001). CONCLUSIONS: The use of the DuoStim strategy in poor-prognosis patients undergoing PGT-A cycles maintains a similar euploidy rate while reducing the time required to obtain a euploid blastocyst.
Asunto(s)
Pruebas Genéticas , Diagnóstico Preimplantación , Femenino , Embarazo , Humanos , Blastocisto/fisiología , Aneuploidia , Embrión de Mamíferos , Estudios Retrospectivos , Fertilización In VitroRESUMEN
Mutations in the DYNAMIN2 (DNM2) gene are frequently detected in human acute T-cell lymphoblastic leukemia (T-ALL), although the mechanisms linking these mutations to disease pathogenesis remain unknown. Using an ENU-based forward genetic screen for mice with erythroid phenotypes, we identified a heterozygous mouse line carrying a mutation in the GTPase domain of Dnm2 (Dnm2V265G) that induced a microcytic anemia. In vitro assays using the V265G mutant demonstrated loss of GTPase activity and impaired endocytosis that was comparable to other DNM2 mutants identified in human T-ALL. To determine the effects of DNM2 mutations in T-ALL, we bred the Dnm2V265G mice with the Lmo2 transgenic mouse model of T-ALL. Heterozygous Dnm2 mutants lacking the Lmo2 transgene displayed normal T-cell development, and did not develop T-ALL. In contrast, compound heterozygotes displayed an accelerated onset of T-ALL compared with mice carrying the Lmo2 oncogene alone. The leukemias from these mice exhibited a more immature immunophenotype and an expansion in leukemic stem cell numbers. Mechanistically, the Dnm2 mutation impaired clathrin-mediated endocytosis of the interleukin (IL)-7 receptor resulting in increased receptor density on the surface of leukemic stem cells. These findings suggest that DNM2 mutations cooperate with T-cell oncogenes by enhancing IL-7 signalling.
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Dinamina II/genética , Interleucina-7/metabolismo , Leucemia de Células T/etiología , Mutación , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Endocitosis/genética , GTP Fosfohidrolasas/metabolismo , Humanos , Proteínas con Dominio LIM/genética , Leucemia de Células T/genética , Leucemia de Células T/metabolismo , Ratones , Oncogenes , Transducción de SeñalRESUMEN
Notch signaling is essential for definitive hematopoiesis, but its role in human embryonic hematopoiesis is largely unknown. We show that in hESCs the expression of the Notch ligand DLL4 is induced during hematopoietic differentiation. We found that DLL4 is only expressed in a sub-population of bipotent hematoendothelial progenitors (HEPs) and segregates their hematopoietic versus endothelial potential. We demonstrate at the clonal level and through transcriptome analyses that DLL4(high) HEPs are enriched in endothelial potential, whereas DLL4(low/-) HEPs are committed to the hematopoietic lineage, albeit both populations still contain bipotent cells. Moreover, DLL4 stimulation enhances hematopoietic differentiation of HEPs and increases the amount of clonogenic hematopoietic progenitors. Confocal microscopy analysis of whole differentiating embryoid bodies revealed that DLL4(high) HEPs are located close to DLL4(low/-) HEPs, and at the base of clusters of CD45+ cells, resembling intra-aortic hematopoietic clusters found in mouse embryos. We propose a model for human embryonic hematopoiesis in which DLL4(low/-) cells within hemogenic endothelium receive Notch-activating signals from DLL4(high) cells, resulting in an endothelial-to-hematopoietic transition and their differentiation into CD45+ hematopoietic cells.
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Biomarcadores/metabolismo , Diferenciación Celular , Células Madre Embrionarias/citología , Endotelio/citología , Hematopoyesis/fisiología , Células Madre Hematopoyéticas/citología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas de la Membrana/metabolismo , Animales , Proliferación Celular , Células Cultivadas , Cuerpos Embrioides , Células Madre Embrionarias/metabolismo , Endotelio/metabolismo , Femenino , Citometría de Flujo , Perfilación de la Expresión Génica , Células Madre Hematopoyéticas/metabolismo , Humanos , Técnicas para Inmunoenzimas , Péptidos y Proteínas de Señalización Intracelular/genética , Proteínas de la Membrana/genética , Ratones , Ratones Endogámicos NOD , Ratones SCID , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Increasing evidence suggests that mesenchymal stem/stromal cells (MSCs) carrying specific mutations are at the origin of some sarcomas. We have reported that the deficiency of p53 alone or in combination with Rb (Rb(-/-) p53(-/-)) in adipose-derived MSCs (ASCs) promotes leiomyosarcoma-like tumors in vivo. Here, we hypothesized that the source of MSCs and/or the cell differentiation stage could determine the phenotype of sarcoma development. To investigate whether there is a link between the source of MSCs and sarcoma phenotype, we generated p53(-/-) and Rb(-/-)p53(-/-) MSCs from bone marrow (BM-MSCs). Both genotypes of BM-MSCs initiated leiomyosarcoma formation similar to p53(-/-) and Rb(-/-)p53(-/-) ASCs. In addition, gene expression profiling revealed transcriptome similarities between p53- or Rb-p53-deficient BM-MSCs/ASCs and muscle-associated sarcomagenesis. These data suggest that the tissue source of MSC does not seem to determine the development of a particular sarcoma phenotype. To analyze whether the differentiation stage defines the sarcoma phenotype, BM-MSCs and ASCs were induced to differentiate toward the osteogenic lineage, and both p53 and Rb were excised using Cre-expressing adenovectors at different stages along osteogenic differentiation. Regardless the level of osteogenic commitment, the inactivation of Rb and p53 in BM-MSC-derived, but not in ASC-derived, osteogenic progenitors gave rise to osteosarcoma-like tumors, which could be serially transplanted. This indicates that the osteogenic differentiation stage of BM-MSCs imposes the phenotype of in vivo sarcoma development, and that BM-MSC-derived osteogenic progenitors rather than undifferentiated BM-MSCs, undifferentiated ASCs or ASC-derived osteogenic progenitors, represent the cell of origin for osteosarcoma development.
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Carcinogénesis , Diferenciación Celular , Células Madre Mesenquimatosas/patología , Fenotipo , Proteína de Retinoblastoma/deficiencia , Sarcoma/patología , Proteína p53 Supresora de Tumor/deficiencia , Tejido Adiposo/patología , Animales , Células de la Médula Ósea/patología , Ciclo Celular , Eliminación de Gen , Regulación Neoplásica de la Expresión Génica , Leiomiosarcoma/genética , Leiomiosarcoma/metabolismo , Leiomiosarcoma/patología , Ratones , Osteogénesis , Osteosarcoma/genética , Osteosarcoma/metabolismo , Osteosarcoma/patología , Proteína de Retinoblastoma/genética , Sarcoma/genética , Sarcoma/metabolismo , Proteína p53 Supresora de Tumor/genéticaRESUMEN
In Spain, hazardous household waste management by citizens occurs via fixed recycling centres (FRC) and mobile recycling centres (MRC) which usually depend on local governments. This paper addresses a request by the Madrid City Council, in an attempt to improve the service it provides to the city of Madrid. The aim of the study involved analysing the information people possess in relation to hazardous waste and to the use of available equipment, and conducting a post-evaluation of the effectiveness of an environmental communication campaign conducted by the Madrid City Council and aimed at providing awareness of the existence of new FRCs and MRCs. To this end, a questionnaire was conducted with 5644 inhabitants of the city of Madrid. Qualitative data was categorized using content analysis followed by chi-squared tests, considering some socio-demographic characteristics of the sample, such as age or place of residence (district). Communication campaigns influenced citizen awareness of what constituted hazardous waste, of how to properly separate waste and of the existence of FRCs and MRCs. However, few citizens actually used FRCs or MRC (18% across four districts), a fact that might be related to a lack of knowledge of downstream waste treatment issues, or to self-limiting hindrances to householders, such as distance to recycling centres. It is recommended that future communication campaigns investigate householder needs and pre-conceptions in relation to recycling, as well as tailored education aimed at addressing the barriers, perceived or otherwise, facing citizens.
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Participación de la Comunidad , Residuos Peligrosos , Administración de Residuos/métodos , Adolescente , Adulto , Factores de Edad , Distribución de Chi-Cuadrado , Ciudades , Participación de la Comunidad/estadística & datos numéricos , Composición Familiar , Humanos , Persona de Mediana Edad , Opinión Pública , Reciclaje , España , Encuestas y Cuestionarios , Administración de Residuos/estadística & datos numéricos , Adulto JovenRESUMEN
Experimental and clinical data strongly suggest that aldosterone may contribute to proteinuria and progressive renal disease. In fact, an aldosterone antagonist seems to be effective for controlling proteinuria in native kidneys. However, there is little information about this approach in renal transplant patients, a population in whom the presence and amount of proteinuria represent risk factors for graft loss, cardiovascular disease, and death. The aim of our study was to evaluate whether addition of an aldosterone antagonist, spironolactone, provided an additional antiproteinuric effect to the angiotensin-converting enzyme inhibitor (ACEI) and angiotensin type I receptor antagonists (ARB). We evaluated the effects on severe proteinuria (4.4±1.4 g/d) at 6 months after prescription of spironolactone (25 mg/d) among 11 renal transplant patients with serum creatinine values less than 3 mg/dL who were under treatment with an ACEI plus an ARB. Patients were examined in the renal transplant outpatient clinic every week for the first month and twice a month thereafter. Nine patients showed a more than 50% (mean=81.5%) reduction in proteinuria not only early, but also sustained at 6 months (4.4±1.4 to 2.3±1.1 g/d) with a mild, nonsignificant deterioration in renal function (serum creatinine 1.6±0.32 to 1.7±0.54 mg/dL). This study showed that spironolactone decreased severe proteinuria among patients treated with an ACEI plus an ARB. This therapy is not recommended for patients with glomerular filtration rates below 40 mL/min. Therefore, it is suggested that using triple blockade of RAS is feasible in selected renal transplant patients to reduce proteinuria, although caution is required to avoid severe hyperkalemia.
Asunto(s)
Bloqueadores del Receptor Tipo 1 de Angiotensina II/uso terapéutico , Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Trasplante de Riñón , Antagonistas de Receptores de Mineralocorticoides/uso terapéutico , Proteinuria/prevención & control , Sistema Renina-Angiotensina/efectos de los fármacos , Espironolactona/uso terapéutico , Adulto , Bloqueadores del Receptor Tipo 1 de Angiotensina II/administración & dosificación , Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Inhibidores de la Enzima Convertidora de Angiotensina/administración & dosificación , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Terapia Combinada , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Antagonistas de Receptores de Mineralocorticoides/administración & dosificación , Antagonistas de Receptores de Mineralocorticoides/farmacología , Proyectos Piloto , Espironolactona/administración & dosificación , Espironolactona/farmacologíaRESUMEN
The methanol soluble fraction of the aqueous extract obtained from the dry heads of Centaurea diffusa demonstrated antimicrobial activity in twelve evaluated microorganisms.
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Antiinfecciosos/farmacología , Centaurea , Extractos Vegetales/farmacología , Bacterias/efectos de los fármacos , Candida albicans/efectos de los fármacos , Copas de Floración , Pruebas de Sensibilidad MicrobianaRESUMEN
This paper describes a rapid, sensitive and specific method for determination of free amino acids in honey involving a new reaction of derivatization and gas chromatography (GC) with flame ionization (FID) and mass spectrometric (MS) detection. The method allows the determination of 22 free amino acids in honey samples in a short time: 8 and 5 min for GC-FID and GC-MS, respectively. Quantitation was performed using Norvaline as internal standard, with detection limits ranging between 0.112 and 1.795 mg/L by GC-FID and between 0.001 and 0.291 mg/L by GC-MS in the selected-ion monitoring mode. The method was validated and applied to a set of 74 honey samples belonging to four different botanical origins: eucaliptus, rosemary, orange and heather. The statistical treatment of data shows a correct classification of different origins over 90%.
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Aminoácidos/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Miel/análisis , Sensibilidad y EspecificidadRESUMEN
A transformation system for selected mature cork oak (Quercus suber L.) trees using Agrobacterium tumefaciens has been established. Embryos obtained from recurrent proliferating embryogenic masses were inoculated with A. tumefaciens strains EHA105, LBA4404 or AGL1 harbouring the plasmid pBINUbiGUSint [carrying the neomycin phosphotransferase II (nptII) and beta-glucuronidase (uidA) genes]. The highest transformation efficiency (4%) was obtained when freshly isolated explants were inoculated with A. tumefaciens strain AGL1. Evidence of stable transgene integration was obtained by PCR for the nptII and uidA genes, Southern blotting and expression of the uidA gene. The transgenic embryos were germinated and successfully transferred to soil.
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Agrobacterium tumefaciens/genética , Vectores Genéticos/genética , Plantas Modificadas Genéticamente/genética , Quercus/genética , Transformación Genética/genética , Factores de Edad , Desarrollo Embrionario/genética , Glucuronidasa/genética , Kanamicina Quinasa/genética , Plantas Modificadas Genéticamente/embriología , Plantas Modificadas Genéticamente/microbiología , Plásmidos/genética , Quercus/embriología , Quercus/microbiología , Semillas/genética , Semillas/crecimiento & desarrollo , Semillas/microbiología , Transfección/métodos , Transgenes/genéticaRESUMEN
Centaurea solstitialis y Centaurea calcitrapa (Asteraceae), son plantas conocidas vulgarmente como Abrepuño amarillo y Abrepuño colorado respectivamente. Son malezas que se desarrollan en la región pampeana, siendo la primera de ellas la más abundante. Investigaciones realizadas en otros países han demostrado que el género Centaurea posee propiedades antimicrobianas. El objetivo de este trabajo fue comprobar si esta actividad biológica se encuentra presente en las malezas que crecen en la provincia de La Pampa (Argentina). Se evaluó la Concentración Inhibitoria Mínima y la Concentración Bactericida Mínima mediante el método de dilución en caldo de extractos metanólicos de capítulos secos de ambas especies. Los resultados obtenidos demuestran que Centaurea calcitrapa, bajo nuestras condiciones de trabajo, presenta actividad antimicrobiana en cuatro de las diez cepas ensayadas (Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus agalactiae y Salmonella typhimurium), mientras que Centaurea solstitialis muestra menor actividad antibacteriana inhibiendo sólo a dos cepas (Streptococcus agalactiae y Staphylococcus aureus) (AU)
Centaurea solstitialis and Centaurea calcitrapa (Asteraceae), commonly known as Abrepuño amarillo and Abrepuño colorado respectively, are weeds that grow in the Province of Pampea Argentina, the former of which being the most abundantly encountered species. Research carried out in other countries has demonstrated that the genus Centaurea possesses antimicrobial properties. The objective of this work was to ascertain the extent to which such a biological activity may be present in these species, found growing in this particular Argentinian Province. Minimum Inhibitory Concentration and Minimum Bactericide Concentration was evaluated by means of the dilution method, in broth of methanolic extracts of dry heads of both species. The results obtained, under the working conditions of this study, demonstrated that Centaurea calcitrapa, presents antimicrobial activity against four of the ten assayed strains: Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus agalactiae and Salmonella typhimurium, while Centaurea solstitialis shows antibacterial activity to a lesser extent, with inhibitory activity only being found against two strains: Streptococcus agalactiae and Staphylococcus aureus (AU)
Asunto(s)
Humanos , Antibacterianos/farmacocinética , Centaurea , Extractos Vegetales/farmacocinética , Metanol/farmacología , Pruebas de Sensibilidad Microbiana/métodosRESUMEN
The regeneration of somatic seedlings from selected 100-year-old cork oak trees is reported. The induction of somatic embryogenesis from leaves of epicormic shoots was significantly affected by genotype, harvesting time and their interaction. Leaves from all five selected trees produced somatic embryos when the segments of branches used as sources of epicormic shoots were collected in May. Genotype, but not the level of photosynthetically active radiation, affected the proliferation of the embryogenic lines and the number of detachable embryos that could be obtained from them. Genotype also affected several steps leading to conversion of somatic embryos, from germination to complete acclimatisation of somatic seedlings. Almost 40% of the somatic embryos from all lines germinated, showing coordinated root and shoot growth. Although the mean percentage of recovery for the whole process was low, plants could be regenerated from four of the five trees tested.
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Hojas de la Planta/embriología , Quercus/embriología , Semillas/crecimiento & desarrollo , Aclimatación/genética , Aclimatación/fisiología , Células Clonales , Técnicas de Cultivo/métodos , Genotipo , Fotosíntesis/fisiología , Raíces de Plantas/embriología , Brotes de la Planta/embriología , Quercus/genética , Semillas/embriología , Factores de TiempoRESUMEN
Somatic embryogenesis was induced in expanding leaves from epicormic shoots forced to sprout from segments of branches collected from several hundred-year-old cork oak trees. Following a basic protocol previously defined for leaves taken from seedlings of this species, several factors were studied to improve the response. The induction frequency was significantly higher when the length of exposure to growth regulators was increased from 7 to 30 days. The combined application of NAA and BAP was essential for induction. Although both regulators had a very significant influence, their interaction was not significant, suggesting independent roles. Leaf size had a crucial effect, because beyond a certain threshold, embryogenesis could not be obtained. Embryogenic lines were maintained via repetitive embryogenesis on hormone-free medium for more than 2 years.
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Adenina/análogos & derivados , Quercus/embriología , Semillas/crecimiento & desarrollo , Adenina/farmacología , Compuestos de Bencilo , Técnicas de Cultivo/métodos , Cinetina , Ácidos Naftalenoacéticos/farmacología , Reguladores del Crecimiento de las Plantas/farmacología , Purinas , Quercus/efectos de los fármacos , Semillas/efectos de los fármacos , Semillas/genéticaRESUMEN
Several models are proposed for T-cell antigen receptor (TCR) assembly and structure. However, there is little experimental data favouring directly either one or the other(s). The minimal complex appears to be composed of a TCRalphabeta/CD3deltaepsilon,gammaepsilon/zeta2 structure but at the cell membrane, multimers of this minimal structure may be formed. Quantitative cytofluometry has suggested three CD3epsilon chains for two TCRbeta (or TCRdelta) chains/complex. Such data should be repeated with monoclonal antibodies (MoAb) against extracellular (EC) parts of CD3delta or CD3gamma chains. In the present review, we have compared the TCR/CD3 assembly of pre-TCR, TCRgammadelta and TCRalphabeta containing complexes, and analysed the reactivity of antibodies (Abs) against the EC part of CD3delta chains. Our data suggest an alternative assembly pathway and structure of TCR/CD3 complexes.
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Receptores de Antígenos de Linfocitos T/química , Animales , Anticuerpos , Complejo CD3/química , Complejo CD3/metabolismo , Humanos , Sustancias Macromoleculares , Modelos Inmunológicos , Modelos Moleculares , Receptores de Antígenos de Linfocitos T/metabolismo , Receptores de Antígenos de Linfocitos T alfa-beta/química , Receptores de Antígenos de Linfocitos T alfa-beta/metabolismo , Receptores de Antígenos de Linfocitos T gamma-delta/química , Receptores de Antígenos de Linfocitos T gamma-delta/metabolismoRESUMEN
Functional rearrangement at the TCRbeta locus leads to surface expression on developing pre-T cells of a pre-TCR complex composed of the TCRbeta-chain paired with the invariant pre-TCRalpha (pTalpha) chain and associated with CD3 components. Pre-TCR signaling triggers the expansion and further differentiation of pre-T cells into TCRalphabeta mature T cells, a process known as beta selection. Besides the conventional pTalpha transcript (termed pTalpha(a)), a second, alternative spliced, isoform of the pTalpha gene (pTalpha(b)) has been described, whose developmental relevance remains unknown. In this study, phenotypic, biochemical, and functional evidence is provided that only pTalpha(a) is capable of inducing surface expression of a CD3-associated pre-TCR complex, which seems spontaneously recruited into lipid rafts, while pTalpha(b) pairs with and retains TCRbeta intracellularly. In addition, by using real-time quantitative RT-PCR approaches, we show that expression of pTalpha(a) and pTalpha(b) mRNA spliced products is differentially regulated along human intrathymic development, so that pTalpha(b) transcriptional onset is developmentally delayed, but beta selection results in simultaneous shutdown of both isoforms, with a relative increase of pTalpha(b) transcripts in beta-selected vs nonselected pre-T cells in vivo. Relative increase of pTalpha(b) is also shown to occur upon pre-T cell activation in vitro. Taken together, our data illustrate that transcriptional regulation of pTalpha limits developmental expression of human pre-TCR to intrathymic stages surrounding beta selection, and are compatible with a role for pTalpha(b) in forming an intracellular TCRbeta-pTalpha(b) complex that may be responsible for limiting surface expression of a pTalpha(a)-containing pre-TCR and/or may be competent to signal from a subcellular compartment.