The combined coronal-transconjunctival approach: an innovative surgical access for orbital exenteration in craniofacial resection

Malignant tumours arising in the paranasal sinuses or maxilla usually spread to the surrounding regions. The skull base and the anterior cranial fossa are frequently affected as well. When the resection of a tumour involves an orbital exenteration, a transconjunctival-perilimbic incision can be added to a coronal approach in order to preserve the eyelids and the conjunctiva, avoiding cutaneous midfacial incisions. Patients with a diagnosis of malignant tumour affecting the orbit, upper jaw, paranasal sinuses, and/or anterior skull base were eligible for this technique. Tumoural invasion of the eyelids, conjunctiva, lacrimal system, or surrounding skin was considered a contraindication for this technique. A retrospective study of the clinical records was performed and age, type of tumour, location, and reconstructive technique were evaluated. Eight patients referred to the study department between 2015 and 2019 were selected. All patients underwent craniofacial surgery and orbital exenteration. The transconjunctival-perilimbic approach was combined with a coronal incision in all cases. In our experience, the transconjunctival-perilimbic approach to orbital exenteration proposed in this paper can be used successfully in skull base surgery. Combined with a coronal and transmandibular approach, it allows wide access to the facial skeleton/anterior skull base while avoiding skin incisions in the midface.

Chondrocytes extract from patients with osteoarthritis induces chondrogenesis in infrapatellar fat pad-derived stem cells

OBJECTIVE

Infrapatellar fat pad of patients with osteoarthritis (OA) contains multipotent and highly clonogenic adipose-derived stem cells that can be isolated by low invasive methods. Moreover, nuclear and cytoplasmic cellular extracts have been showed to be effective in induction of cell differentiation and reprogramming. The aim of this study was to induce chondrogenic differentiation of autologous mesenchymal stem cells (MSCs) obtained from infrapatellar fat pad (IFPSCs) of patients with OA using cellular extracts-based transdifferentiation method.

DESIGN

IFPSCs and chondrocytes were isolated and characterized by flow cytometry. IFPSCs were permeabilized with Streptolysin O and then exposed to a cell extract obtained from chondrocytes. Then, IFPSCs were cultured for 2 weeks and chondrogenesis was evaluated by morphologic and ultrastructural observations, immunologic detection, gene expression analysis and growth on 3-D poly (dl-lactic-co-glycolic acid) (PLGA) scaffolds.

RESULTS

After isolation, both chondrocytes and IFPSCs displayed similar expression of MSCs surface makers. Collagen II was highly expressed in chondrocytes and showed a basal expression in IFPSCs. Cells exposed to chondrocyte extracts acquired a characteristic morphological and ultrastructural chondrocyte phenotype that was confirmed by the increased proteoglycan formation and enhanced collagen II immunostaining. Moreover, chondrocyte extracts induced an increase in mRNA expression of chondrogenic genes such as Sox9, L-Sox5, Sox6 and Col2a1. Interestingly, chondrocytes, IFPSCs and transdifferentiated IFPSCs were able to grow, expand and produce extracellular matrix (ECM) on 3D PLGA scaffolds.

CONCLUSIONS

We demonstrate for the first time that extracts obtained from chondrocytes of osteoarthritic knees promote chondrogenic differentiation of autologous IFPSCs. Moreover, combination of transdifferentiated IFPSCs with biodegradable PLGA 3D scaffolds can serve as an efficient system for the maintenance and maturation of cartilage tissue. These findings suggest its usefulness to repair articular surface in OA.

Purification and long-term expansion of multipotent endothelial-like cells with potential cardiovascular regeneration

Endothelial progenitor cells (EPC) represent a relatively rare cell population, and expansion of sufficient cell numbers remains a challenge. Nevertheless, human adipose-derived stem cells (hASC) can be easily isolated and possess the ability to differentiate into endothelial cells. Here, we propose the isolation and characterization of multipotent endothelial-like cells (ME-LC) with the capacity to maintain their vascular progenitor properties for long periods. hASC were isolated from lipoaspirates and cultured through distinct consecutive culture stages for 2 months to enrich ME-LC: first in Dulbecco's modified Eagle's medium-fetal bovine serum (stage I), followed by a stage of culture in absent of fetal bovine serum (stage II), a culture in SFO3 medium (stage III), and, finally, the culture of ME-LC into collagen IV-coated flasks in endothelial growth medium (EGM-2) (stage IV). ME-LC display increased expression levels of endothelial and hematopoietic lineage markers (CD45, KDR, and CXCR4) and EPC markers (CD34 and CD133), whereas the expression of CD31 was barely detectable. Reverse transcription (RT)-polymerase chain reaction assays showed expression of genes involved in early stages of EPC differentiation and decreased expression of genes associated to differentiated EPC (TIE-2, DLL4, and FLT-1). ME-LC formed capillary-like structures when grown on Matrigel, secreted increased levels of stromal cell-derived factor-1 (SDF-1), and showed the ability to migrate attracted by SDF-1, vascular endothelial growth factor, and hematopoietic growth factor cytokines. Importantly, ME-LC retained the capacity to differentiate into cardiomyocyte-like cells. We present a simplified and efficient method to generate large numbers of autologous ME-LC from lipoaspirates-derived hASC, opening up potential cell-based therapies for cardiovascular regenerative medicine.

Promotion of human adipose-derived stem cell proliferation mediated by exogenous nucleosides

Adult stem cells are becoming the best option for regenerative medicine because they have low tumourigenic potential and permit autologous transplantation, even without in vitro culture. Our objectives were to evaluate the effects of exogenous nucleosides on the proliferation of hASCs (human adipose-derived stem cells), with or without co-treatment with 5-aza (5-azacytidine), and to analyse the expression of lamin A/C during cardiomyocyte differentiation of these cells. We isolated hASCs from human lipoaspirates that were positive for mesenchymal stem cell markers. We found that 5-aza induces a dose-dependent inhibition of hASC proliferation [IC50 (inhibitory concentration 50): 5.37 microM], whereas exogenous nucleosides significantly promote the proliferation of hASCs and partially revert the antiproliferative effect of the drug. Multipotentiality of isolated hASCs was confirmed by adipogenic, osteogenic and cardiomyogenic induction. 5-Aza-induced cells expressed cardiac troponins I and T and myosin light chain 2, myocardial markers that were directly correlated with lamin A/C expression. Our results support the importance of the nucleoside supplementation of media to improve conditions for the expansion and maintenance of hASCs in culture. In addition, the quantification of lamin A/C expression appears to be a good marker for the characterization of cardiomyocyte differentiation of stem cells that has rarely been used.

Fatal lipoid pneumonia due to bronco-aspiration of isoparaffin after ingestion of an organophosphate insecticide

A 66-year-old-male patient with a history of depression voluntarily ingested around 400 ml of an insecticide composed of 5% methylparathion, 75% isoparaffin, 8% etoxylated oleic acid, 4% 1,2,4-trimethylbenzene, 6% naphtha, 1% 1,3,5- trimethylbenzene, 0.4% propylbenzene and 0.3% xylene. The patient was conscious and alert at admission. Gastric lavage was performed and activated charcoal administered. There were no clinical symptoms of organophospate ingestion despite reduced concentrations of erythrocyte and plasma cholinesterase. Chest X-ray showed pulmonary infiltrate compatible with bronco-aspiration. The patient evolved to respiratory failure refractory to treatment and died from multiorganic failure 23 days after ingesting the insecticide. The pathological findings included a pulmonary fibrosis in the alveolar spaces which caused enlargement of the intra-alveolar septa. Abundant lipin-laden macrophages were observed within the alveolar spaces. We review the most relevant aspects of cases of fatal lipoid pneumonia and point out that on occasion severe or fatal intoxication is due to the substances accompanying the active ingredients.

Combined isolation of CD34+ progenitor cells and reduction of B cells from peripheral blood by use of immunomagnetic methods

BACKGROUND

Malignant cells may contribute to relapse after autologous hematopoietic cell transplantation The effectiveness of a double immunomagnetic purging strategy combining CD34-positive with B-negative cell selection to purge peripheral blood progenitor cells (PBPCs) from patients with chronic lymphoproliferative disorders has been analyzed.

STUDY DESIGN AND METHODS

Twenty-two CD34+ cell selections from patients with follicular lymphoma (n = 14), chronic lymphocytic leukemia (n = 6), mantle cell lymphoma (n = 1), and splenic marginal zone lymphoma (n = 1) were performed by use of a magnetic cell selector followed by a negative cell selection step with anti-CD19 monoclonal antibody bound to immunomagnetic beads.

RESULTS

The PBPC components contained median CD34+ cells of 1.24 percent (range, 0.38-3.92%) and CD19+ cells of 1.83 percent (range, 0.06-69.7%). After positive selection (n = 22), 49 percent (range, 16-72%) of CD34+ cells were recovered with a purity of 93 percent (range, 24-99%). The double-positive and -negative selections (n = 20) yielded 57.5 percent of CD34+ cells (range, 33.4-79.4%) with a purity of 95 percent (range, 63-99%). Logarithms of B-cell reduction in the CD34+-cell-enriched B-cell-depleted component had a median value of 3.63 (range, 2.74-4.84 log) and CD19+ and CD5+ cells for chronic lymphocytic leukemia patients with more than 4.56 log (>3.6-5.6 log). Of 13 PBPC components that had a tumor-specific clonal signal, 10 became PCR negative after the double-selection procedure.

CONCLUSION

Combined positive and negative magnetic cell selection achieves a high grade of tumor cell reduction with up to 77 percent of the grafts being negative for tumor-specific clonal signal by PCR analysis. This technique preserves an adequate recovery of progenitor cells able to engraft.

Acute quadriplegic myopathy with loss of thick (myosin) filaments following heart transplantation

Acute quadriplegic myopathy with loss of thick (myosin) filaments (AQM-LTF) is an acute toxic myopathy observed in critically ill patients and is characterized by proximal or diffuse weakness of extremities and difficulty in weaning from mechanical ventilation. In recent years, this myopathy has been described in transplanted patients, although only 5 cases have been reported following heart transplantation. We present 3 new cases and review the previous literature. We conclude that the clinical picture and outcome of AQM-LTF in heart-transplanted patients do not differ from those observed in other critically ill patients (transplanted and non-transplanted). Therefore, because AQM-LTF is often clinically suspected muscle biopsy should be quickly performed to confirm the diagnosis so that physical therapy may begin as soon as possible.

Mitochondrial involvement in antiretroviral therapy-related lipodystrophy

OBJECTIVES

The management of HIV infection has greatly improved during recent years essentially because of the appearance of new antiretroviral drugs. Highly active antiretroviral therapy (HAART) has achieved important reductions of viraemia and significant recoveries of CD4(+) cell counts in HIV-infected patients. Nonetheless, cases of HIV-infected individuals experiencing lipodystrophy (LD) are being increasingly reported. The purpose of this work was to analyse whether the presence of mitochondrial abnormalities is a frequent feature in LD, since we previously detected mitochondrial abnormalities in an HIV-patient. The second main objective was to study whether LD could be associated with a specific drug.

DESIGN

Seven HIV patients presenting LD and five HIV non-LD controls participated in the study. LD patients met the following criteria: (1) LD was their only clinical abnormality, (2) LD was clinically relevant, (3) compliance with antiretroviral treatment was higher than 90% and (4) patients did not have personal or familial history suggestive of mitochondrial disease or neuromuscular disorder.

METHODS

Histological stainings, histo-enzymatic reactions, enzymatic and respiratory activities of mitochondrial respiratory chain complexes, and mitochondrial DNA (mtDNA) depletion and rearrangements were examined on muscle mitochondria.

RESULTS

Structural muscle abnormalities, mitochondrial respiratory chain dysfunction or mtDNA deletions were detected in all HIV lipodystrophic patients.

CONCLUSIONS

The mitochondrial abnormalities found suggest that mitochondrial dysfunction could play a role in the development of antiretroviral therapy-related lipodystrophy.

Combined positive and negative cell selection from allogeneic peripheral blood progenitor cells (PBPC) by use of immunomagnetic methods

Twenty-four mobilized peripheral blood products from healthy donors for allogeneic transplantation were positively selected for CD34(+) cells and depleted of CD4(+) and CD8(+) cells (+/- selection) by combining clinical grade immunomagnetic methods. A sequential, "two-step" strategy combining positive selection of CD34(+) cells by use of the Isolex 300i (versions 1 and 2) device and T cell depletion (TCD) using the MaxSep device and a simultaneous, "one-step" method of CD34(+)cell selection and TCD using the Isolex 300i (software versions 1 and 2) have been investigated. Using these magnetic bead separation systems, two groups of sequential +/- selection (Isolex 300i version 1/MaxSep and Isolex 300i version 2/MaxSep) and two groups of simultaneous +/- selection (Isolex 300i versions 1 and 2) were analysed. In the sequential +/- selection, logarithms of TCD (CD3(+) cell depletion) obtained by the positive selection step had median values of 3.7 with the version 1 (n = 5) and 4.5 with version 2 software of the Isolex 300i (n = 5) (P = 0.07). Version 2 also gave a higher CD34(+) cell purity and yield than did version 1 (92% vs77%, P < 0.05 and 55% vs 34%, P = 0.3, respectively). Additional TCD obtained in the second step with the MaxSep device for the two groups had a median value of 0.9 log and 7% CD34(+)cell losses. In the simultaneous +/- selection, the Isolex 300i version 2 (n = 10) gave a median TCD of 5.1 log and version 1 (n = 4) of 4 log (P < 0.005). Higher CD34(+)cell purity and yield were also obtained with version 2 than with version 1 (97% and 76%, P < 0.005 and 57% and 39%, P = 0.07, respectively). These data indicate that simultaneous, "one-step" +/- selection in the Isolex 300i version 2 achieves a high TCD with a high CD34(+) cell purity and an acceptable CD34(+) cell yield.

Isolation of CD34+ progenitor cells from peripheral blood by use of an automated immunomagnetic selection system: factors affecting the results

BACKGROUND

The isolation of CD34+ cells from mobilized peripheral blood is being increasingly used in the setting of allogeneic or autologous hematopoietic cell transplantation. Investigation of variables that may influence the effectiveness of CD34+ cell selection is of interest.

STUDY DESIGN AND METHODS

Fifty-one CD34+ cell selections from peripheral blood progenitor cells (PBPCs) (39 allogeneic and 12 autologous) were performed using a magnetic cell separator (Isolex 300i, Baxter), including version 2.0 software. The results obtained were analyzed for different processing variables. The feasibility of transplanting these isolated CD34+ cells was also analyzed.

RESULTS

The isolated CD34+ cell fraction had a median purity of 88.9 percent (range, 47.8-98.3). The median recovery of CD34+ cells was 45.1 percent (13.8-76.2), and the median colony-forming unit- granulocyte-macrophage (CFU-GM) content was 17. 2 percent (0.8-58.6). Logarithms of T- and B-cell depletion had median values of 3.7 and 2.8, respectively. The version 2.0 software of the Isolex 300i gave a higher CD34+ cell recovery in the enriched cell fraction (median 57.8%) than did version 1.11 (39.4%) or 1.12 (44.4%) (p = 0.01). The use of recombinant human deoxyribonuclease I during cell processing yielded more CD34+ cells (53% vs. 41%, p = 0. 01) and higher purity (92.8% vs. 87%, p = 0.03). There was a correlation between the percentage of CD34+ cells labeled with the monoclonal antibody 8G12 clone and the percentage of CD34+ cells labeled with the monoclonal antibody used during the processing technique (9C5 clone) in the initial, enriched, and depleted CD34+ cell fractions (R(2) = 0.95; 0.92; 0.78, p< 0.005, respectively). Median times for recovering >0.5 x 10(9) per L of granulocytes and >20 x 10(9) per L of platelets were 13 and 16 days in the allograft patients and 13 and 14 days in the autograft patients.

CONCLUSION

CD34+ cells can be highly and effectively isolated from allogeneic and autologous grafts by use of this automated technique, with a high grade of T- and B-cell depletion. These purified CD34+ cell components can engraft normally.

Autologous bone marrow transplantation for high risk acute lymphoblastic leukemia: clinical relevance of ex vivo bone marrow purging with monoclonal antibodies and complement

Herein we describe our experience with 75 consecutive autologous BM transplants for patients with high-risk ALL, with special attention to the clinical impact of BM purging. Fifty-two patients received purged BM using monoclonal antibody (MoAb) cocktails and complement, and 23 patients received untreated BM. The distribution of prognostic factors was similar in both groups. Hemopoietic reconstitution was adequate and did not differ in the two groups. Transplant-related mortality was 9.6% and 13% in 'purged' and 'unpurged' groups. Median follow up was 11 months (2-71) and overall actuarial probability of disease-free survival (DFS) at 5 years was 40% (53% relapse probability). We found a beneficial effect of purging in patients over 15 years of age and in patients needing more than 1 month to reach CR1. Patients in CR1 receiving purged marrow had a longer DFS and a lower relapse probability (52% vs 12%, P = 0.02 and 35% vs 86%, P = 0.005, respectively) which were related to the efficacy of the purging procedure (more or less than one log of depletion). In further CR, no advantage of purging has been found. Our data strongly suggest the clinical relevance of BM purging in autologous BMT in high-risk ALL patients and support the need for prospective randomized studies.

[Self-limited acute encephalopathy related to measles component of viral triple vaccine]

INTRODUCTION

Neurological disorders secondary to the measles component of viral triple vaccine are not frequent. In spite of controversy regarding the cause, the clinical, diagnostic and legal implications are worth considering.

CLINICAL CASE

We present the case of a 16 month-old baby with a clinical picture of self-limiting acute encephalopathy characterized by cerebellar ataxia and alterations in behavior, accompanied by the clinical signs of attenuated measles. The negative results of complementary tests and an obvious time-relationship with a triple virus vaccination lead us to interpret the condition as being secondary to the measles component of the vaccine.

CONCLUSIONS

We consider that although there is a low incidence of complications, the index of suspicion is also low, and even lower in cases with only minor neurological signs. It is therefore possible that such reactions are under-reported.

Immunomagnetic bone marrow (BM) and peripheral blood progenitor cell (PBPC) purging in follicular lymphoma (FL)

Twenty-nine B cell follicular lymphoma (FL) patients had their BM (n = 12) or PBPC (n = 17) purged using a panel of monoclonal antibodies and immunomagnetic beads (IMB). The median recovery of nucleated cells (NC) and CD34+ cells was 59.3% (40.5-74) and 56.1% (30.8-82.9) in BM and 77.2% (64.7-88.3) and 73.5% (61.5-98.6) in PBPC (P<0.0005). A median of >1.62 and >1.02 log of target cell depletion was achieved as judged by flow cytometry analysis in BM and PBPC, respectively. Of 29% of initial harvests that had a bcl2 PCR-amplified signal, 37.5% became PCR negative in the final purged products. Absorbed cells containing IMB-target cell complexes gave bcl2 rearrangement signal in 20% of samples in which the start and final purged components were negative. Twenty-three of 26 patients receiving an autologous purged product are evaluable for engraftment. Median time to reach an ANC >0.5x10(9)/l and platelet count >20x10(9)/l was 21 (11-43) and 41 days (13-70) for BM (n = 9) and 14 (10-31) and 14 (8-37) for PBPC (n = 14) autografted patients (P = 0.01 and 0.001). One patient did not engraft and was rescued with a back-up BM. These data demonstrate that this indirect immunomagnetic technique is able to achieve a high grade of lymphoma cell depletion in BM and PBPC and that these purged products are capable of rapid engraftment after autologous transplantation.

Peripheral blood CD34+ cell immunomagnetic selection in breast cancer patients: effect on hematopoietic progenitor content and hematologic recovery after high-dose chemotherapy and autotransplantation

BACKGROUND

Tumor cells have been detected in mobilized peripheral blood of breast cancer patients, and they may contribute to tumor recurrence after the transplantation of peripheral blood progenitor cells. One of the most widespread technologies for tumor purging of the graft is immunomagnetic hematopoietic progenitor cell selection.

STUDY DESIGN AND METHODS

The study assessed the effectiveness of a magnetic cell-separation system in selecting functional subpopulations of hematopoietic progenitors from 14 blood-derived harvests of 11 patients with high-risk breast cancer after mobilization following cytotoxic chemotherapy supported by granulocyte--colony-stimulating factor, as well as the feasibility of transplanting these selected subpopulations.

RESULTS

CD34(+)-enriched cell fractions had a median purity of 93.0 percent (72.7-98.5%). The procedure yielded 52.6 percent of the CD34+ cell input (39.4-116.8%). Median recoveries of colony-forming units (CFUs) (36.87%) and cobblestone area-forming cells (CAFCs) (152.5%) were, respectively, 0.70 and 2.87 times those of CD34+ cells (52.6%). Moreover, CAFC efficiency in the positive cell fraction was 2.57 times that in the starting cell fraction. Peripheral blood neutrophil counts of 0.5 x 10(9) per L and platelet counts of 20 x 10(9) per L were reached after median times of 9 and 11 days, respectively. The number of transfused CAFCs per kg, CD34+ cells per kg, and postthaw CFU-granulocyte-macrophage per kg was correlated, respectively, with the speed of engraftment of neutrophils, platelets, or both. Tumor cells detected in one patient's peripheral blood were not found after CD34+ cell selection.

CONCLUSION

Transplantation of immunomagnetically purified peripheral blood CD34+ cells does not increase transplantation-related morbidity. It induces a selective enrichment of more immature hematopoietic progenitors, which makes it suitable for use in cell expansion and gene therapy protocols.

Echinococcus granulosus: preparation of protein extracts from protoscolex nuclei for mobility-shift assays

Nuclei from Echinococcus granulosus protoscolices were isolated from infected sheep. Protein extracts were prepared for analysis of DNA-protein interactions involving specific transcriptional regulatory factors. Gel mobility-shift assays were done using a heterologous probe containing binding sites for widespread transcription factors. A fragment of the promoter of GATA-1 transcription factor from the chicken was selected. When nuclear extracts from E. granulosus protoscolices were assayed a specific band shift was observed. The methodologies developed in this study could provide an important contribution for the characterization of the DNA-protein interactions involved in transcriptional regulation within the context of recent developments in the molecular biology of this parasite.

Low-dose donor CD8+ cells in the CD4-depleted graft prevent allogeneic marrow graft rejection and severe graft-versus-host disease for chronic myeloid leukemia patients in first chronic phase

Based on previous experiences in animals and humans, low doses of CD8+ lymphocytes infused together with the marrow graft seem to enhance engraftment after allogeneic T cell-depleted marrow transplantation. From April 1994 to February 1997, 12 patients with chronic myelogenous leukemia in first chronic phase receiving a bone marrow transplant (BMT) from an HLA-identical sibling were included in a pilot study of T cell subset depletion. Total depletion of CD4+ cells of the marrow graft and partial depletion of CD8+ cells was performed by immunomagnetic separation. In order to improve the engraftment rate, we infused a low fixed number of CD8+ lymphocytes (0.25 x 10(6)/kg). All the patients were at high risk of developing acute graft-versus-host disease (GVHD), with a recipient age of >30 years, and/or donor sensitized by previous pregnancies or transfusions. All of them received cyclosporin A and methotrexate post-BMT. No graft failure was observed. The grade III-IV GVHD rate was 16.6%, and the actuarial survival at 3 years is 81.8%. Immunological recovery showed persistent CD8+ HLA-DR+ lymphocytosis 8 months after transplant. Relapses were not observed. This experience shows the importance of CD8+ cells to ensure correct engraftment, decreasing the GVHD rate.

Immunomagnetic bone marrow purging in children with acute lymphoblastic leukemia

Autologous bone marrow transplantation (ABMT) offers a therapeutic alternative for children with poor prognosis acute lymphoblastic leukemia (ALL) who lack an HLA-matched sibling donor. The most common cause of treatment failure after ABMT in these patients is leukemia relapse. We have developed an ex vivo autologous marrow purging program for children with ALL using an immunomagnetic method. BM purging has been performed in 37 children with ALL (31 B-lineage ALL and 6 T-lineage ALL) following an indirect method, using panels of mouse monoclonal antibodies (MAbs) directed against B or T cell antigens, Dynabeads M-450 (Dynal) coated with sheep antimouse (SAM) antibodies, and the MaxSep Magnetic Cell Separator (Baxter). Purging efficiency has been assessed by flow cytometry. Considering the limit of detection of target cells 0.1%, the median depletion was 2.0 log (range 0.8- > 2.8 log) for the B-lineage ALL and 2.7 (range 2.2- > 2, 9 log) for the T-lineage ALL patients. Twenty-seven patients have been autografted (6 in first complete remission, CR, 13 in second CR, and 8 in third or subsequent CR). Engraftment has been satisfactory in all of them, reaching levels of 500 neutrophils/mm3 and 20,000 platelets/mm3 after a median of 17 (range 12-39) and 30 (range 13-96) days post-ABMT, respectively. In summary, our results show that this immunomagnetic procedure achieves high levels of target cell depletion and can be safely applied to bone marrow purging in childhood ALL patients.

Characterization of a flatworm ribosomal RNA-encoding gene: promoter sequence and small subunit rRNA secondary structure

The transcription start point (tsp) of a ribosomal RNA (rRNA)-encoding gene (rDNA) from Echinococcus granulosus has been mapped at a position located 1.1 kb upstream from the small subunit (SSU) rRNA coding sequence. As expected from the analysis of the putative promoter sequence (-200 to +50), no homology was found with rDNA promoters from other organisms. Nevertheless, some interesting motifs were found. There is a d(T)11 track flanked by an inverted repeat (IR) centered at position -32, which is analogous to the position of the TATA box in promoters transcribed by RNA polymerase II. Two other IR were observed that are also present in the Trypanosoma cruzi rDNA promoter. We have also determined the SSU rDNA sequence and established a secondary structure model. The analysis of the secondary structure strongly suggests that this gene encodes a functional SSU rRNA. The fact that both the promoter and the rRNA coding sequence are derived from the same rDNA repeat indicates that the promoter is also functional.

Regulation of cyclin E transcription by E2Fs and retinoblastoma protein

Cyclin E is critical for the advance of cells through the G1 phase of their growth cycle. Transcription of the cyclin E gene is known to be cell cycle-dependent. We have shown previously that mRNA levels of cyclin E are regulated positively by mitogens and negatively by TGF-beta. Much circumstantial evidence implicates both E2F transcription factors and the retinoblastoma protein (pRB) in the control of cyclin E expression. However, the molecular basis of this control has remained unclear. We report here the cloning of the cyclin E promoter and the identification of several putative E2F binding sites within the promoter sequence. We have found that cell cycle regulation of cyclin E transcription is mediated by E2F binding sites present in the promoter. The activity of this promoter can be regulated negatively by pRB. Our results suggest the operation of a positive-feedback loop in late G1 that functions to ensure continued cyclin E expression and pRB inactivation.

Molecular cloning and characterization of actin genes from Echinococcus granulosus

An Echinococcus granulosus genomic library has been screened with a mouse beta-actin cDNA probe. Two clones carrying DNA fragments of about 15 kb, possibly derived from the same genome region, have been isolated. This 15-kb genomic region includes 2 actin-related sequences (EgactI and EgactII) separated by about 4 kb. The nucleotide sequences of both genes were determined. The EgactI sequence presents no introns, but an intron of 591 bp was observed in the EgactII sequence. The genes potentially encode 375 and 376 amino-acid-long actins, respectively, with a homology of 85.3%. The deduced amino acid sequences from both genes were compared to the actin sequences from other organisms, showing similarities ranging from 63.5% to 90.6%. The nucleotide sequence of a partial actin cDNA clone has been determined. The deduced amino acids sequence showed a homology of 90.3% and 88.0% in relation to the EgactI and EgactII sequences respectively, suggesting the existence of at least one more actin gene in E. granulosus. This hypothesis is reinforced by the number of bands detected in the Southern blot analysis. Experiments based on the amplification of DNA segments using 3'-specific actin primers indicate that the EgactI gene is transcribed in protoscoleces.