Effects of epinephrine, norepinephrine, or the combination of norepinephrine and dobutamine on gastric mucosa in septic shock

OBJECTIVES

To compare in the same patient with septic shock, respective effects of epinephrine, norepinephrine, and the combination of norepinephrine and dobutamine (5 microg/kg/min) on systemic hemodynamic parameters and gastric mucosal perfusion using gastric tonometry and laser-Doppler flowmetry techniques.

DESIGN

Prospective, controlled, randomized, crossover study.

SETTING

University hospital intensive care unit.

PATIENTS

Twelve patients with septic shock.

INTERVENTIONS

Each patient received in a random succession epinephrine, norepinephrine, and norepinephrine plus dobutamine. Dosages of epinephrine and norepinephrine were adjusted to achieve a mean arterial pressure between 70 and 80 mm Hg. A laser-Doppler probe and a tonometer were introduced into the gastric lumen.

MEASUREMENTS AND MAIN RESULTS

The increase in gastric mucosal perfusion detected by laser-Doppler flowmetry was higher with epinephrine and the combination of norepinephrine and dobutamine than with norepinephrine alone (p < .05). In addition, the ratio of gastric mucosal perfusion (local oxygen delivery) to systemic oxygen delivery was increased after norepinephrine plus dobutamine as compared with norepinephrine alone and epinephrine (p< .05). Although values of intramucosal pH and gastroarterial PCO2 tended to be higher with norepinephrine plus dobutamine compared with those obtained with norepinephrine and epinephrine, differences were not statistically significant.

CONCLUSIONS

For the same mean arterial pressure in patients with septic shock, our study showed that administration of epinephrine increased gastric mucosal perfusion more than norepinephrine administration alone. Addition of dobutamine (5 microg/kg/ min) to norepinephrine improved gastric mucosal perfusion. This result could be explained by a vasodilating effect of dobutamine on gastric mucosal microcirculation.

Purification, cDNA cloning, and expression of a new human blood plasma glutamate carboxypeptidase homologous to N-acetyl-aspartyl-alpha-glutamate carboxypeptidase/prostate-specific membrane antigen

We describe the identification, cDNA cloning, and biochemical characterization of a new human blood plasma glutamate carboxypeptidase (PGCP). PGCP was co-purified from human placenta with lysosomal carboxypeptidase, cathepsin A, lysosomal endopeptidase, cathepsin D, and a gamma-interferon-inducible protein, IP-30, using an affinity chromatography on a Phe-Leu-agarose column. A PGCP cDNA was obtained as an expressed sequence tag clone and completed at 5'-end by rapid amplification of cDNA ends polymerase chain reaction. The cDNA contained a 1623-base pair open reading frame predicting a 541-amino acid protein, with five putative Asn glycosylation sites and a 21-residue signal peptide. PGCP showed significant amino acid sequence homology to several cocatalytic metallopeptidases including a glutamate carboxypeptidase II also known as N-acetyl-aspartyl-alpha-glutamate carboxypeptidase or as prostate-specific membrane antigen and expressed glutamate carboxypeptidase activity. Expression of the PGCP cDNA in COS-1 cells, followed by Western blotting and metabolic labeling showed that PGCP is synthesized as a 62-kDa precursor, which is processed to a 56-kDa mature form containing two Asn-linked oligosaccharide chains. The mature form of PGCP was secreted into the culture medium, which is consistent with its intracellular localization in secretion granules. In humans, PGCP is found principally in blood plasma, suggesting a potential role in the metabolism of secreted peptides.

Characterization of two monoclonal antibodies against porcine VCAM-1

Immunization of mice with TNF alpha-activated porcine endothelial cells led to the characterization of two monoclonal antibodies (MAbs), 5F3 and 8A7, specific for porcine VCAM-1. Upon flow cytometry, both antibodies increasingly labeled endothelial cells according to their degree of activation. They bound a band of MW 80 kDa on Western blots of endothelial cells, which is the apparent molecular weight of porcine VCAM-1. It was determined by surface plasmon resonance that the antibodies are directed to different antigenic sites. It was also found that 5F3 competes for binding the antigen with a MAb previously characterized as binding domain 1 of porcine VCAM-1. Subsequently, 5F3, but not 8A7, was found to inhibit the adhesion of human B lymphocyte Ramos cells to porcine endothelial cells in vitro. These antibodies, which do not cross-react with human VCAM-1, might be useful for diagnostic or therapeutic purposes in xenotransplantation.

Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP

In ventilated patients with acute lung injury (ALI) we investigated whether respiratory changes in arterial pulse pressure (DeltaPP) could be related to the effects of PEEP and fluid loading (FL) on cardiac index (CI). Measurements were performed before and after application of a PEEP (10 cm H2O) in 14 patients. When the PEEP-induced decrease in CI was > 10% (six patients), measurements were also performed after FL. Maximal (PPmax) and minimal (PPmin) values of pulse pressure were determined over one respiratory cycle and DeltaPP was calculated: DeltaPP (%) = 100 x ((PPmax - PPmin)/ ([PPmax + PPmin]/2)). PEEP decreased CI from 4.2 +/- 1.1 to 3.8 +/- 1.3 L/min/m2 (p < 0.01) and increased DeltaPP from 9 +/- 7 to 16 +/- 13% (p < 0.01). The PEEP-induced changes in CI correlated with DeltaPP on ZEEP (r = -0.91, p < 0.001) and with the PEEP-induced increase in DeltaPP (r = -0.79, p < 0.001). FL increased CI from 3.5 +/- 1.1 to 4.2 +/- 0.9 L/min/m2 (p < 0.05) and decreased DeltaPP from 27 +/- 13 to 14 +/- 9% (p < 0.05). The FL-induced changes in CI correlated with DeltaPP before FL (r = 0.97, p < 0.01) and with the FL-induced decrease in DeltaPP (r = -0.85, p < 0.05). In ventilated patients with ALI, DeltaPP may be useful in predicting and assessing the hemodynamic effects of PEEP and FL.

Topical indomethacin solution versus dexamethasone solution for treatment of inflamed pterygium and pinguecula: a prospective randomized clinical study

PURPOSE

To compare the effect of topical indomethacin 0.1% solution with the effect of topical dexamethasone 0.1% phosphate solution on signs and symptoms of inflamed pterygium and pinguecula.

METHODS

Of 50 consecutive patients who had inflamed pterygia (n = 17) or pingueculae (n = 33), met the study criteria, and signed an informed consent, one eye of each patient was evaluated in a comparative, prospective, randomized, double-masked, controlled study. Objective signs (conjunctival congestion, redness and edema, and staining of cornea) and subjective complaints (photophobia, pain, foreign-body sensation, discomfort, and tearing) were evaluated and scored. We also evaluated "total signs," "total symptoms," and "total score." Group 1 (n = 25) received topical indomethacin 0.1% solution, and group 2 (n = 25) received a topical dexamethasone phosphate 0.1% solution six times daily for 3 days, then four times daily over the following 11 days. Patients were examined before treatment, on days 3, 7, and 14 after the treatment was initiated, and 2 and 4 weeks after the treatment was discontinued.

RESULTS

In both groups, the scores for "total signs," "total symptoms," and "total score" were significantly lower (P = .001) by day 14. There were no differences between groups 1 and 2 for "total signs," "total symptoms," and "total score" at days 3, 7, and 14 (P = .07 to P = .88). After treatment was discontinued, the dexamethasone-treated group experienced a significantly greater recurrence of "total signs" (P = .023 at day 30, P = .02 at day 45), but there was no statistically significant difference in "total symptoms" and "total score." Patients in group 2 reported more stinging after drops were administered than patients in group 1 (P = .002).

CONCLUSIONS

This study indicates that topical indomethacin 0.1% solution is as effective as topical dexamethasone phosphate 0.1% solution for the treatment of inflamed pterygium and pinguecula and, therefore, is suggested as an effective treatment for these conditions.

[Organ procurement from cardiac arrest donors: outcome of kidney grafts and recommendations]

OBJECTIVES

To compare literature data with results obtained with organs procured from donors who died from cardiac arrest and to make proposals for this mode of organ procurement in France.

METHODS

Over the last 10 years, 10 organ donors (2%) among a series of 486 donors in a state of brain death, had died of cardiac arrest. The arrest were perfused with double-balloon catheters. The outcome of the subsequent kidney grafts was compared with data in the literature.

RESULTS

Fifteen of the 18 kidneys from cardiac arrest donors were functioning 1 month after implantation compared with 17 of the 20 kidneys from braindeath donors with beating hearts. The rate of acute tubular necrosis was 55% in the cardiac arrest kidneys and 40% in the beating-heart kidneys. Serum creatinine at 1 yeart was 145 +/- 69 mumol/l 17 +/- 29 mumol/l respectively.

DISCUSSION

These results and those reported in the literature demonstrate that kidney procurement from cardiac arrest donors is feasible. If intensive care and surgery units are well organized, this type of organ procurement could provide a larger number of organs for transplantation. Emergency teams must be available for preparing and transferring the organs.

Spi-1/PU.1 proto-oncogene induces opposite effects on monocytic and erythroid differentiation of K562 cells

Spi-1/PU.1 is a hematopoietic transcription factor of the Ets family. To analyze the effects of ectopic expression of spi-1 on the proliferation/differentiation of human myeloid leukemia cells, K562 cells were stably transfected with a spi-1 expression vector. The transfected cell lines expressed elevated levels of spi-1 mRNA and protein and high Spi-1-DNA binding activity. The spi-1 transfected cells showed reduced growth rates and reduced clonogenic cell growth. When the erythroid and monocytic differentiation markers were analyzed, spi-1 overexpression resulted in opposite effects: erythroid differentiation was significantly inhibited in spi-1 transfectants, while spi-1 overexpression increased the monocytic differentiation of cells. These results indicate a differential role of Spi-1 on the differentiation of human myeloid leukemia cells.

Treatment of Ph1-positive chronic myelogenous leukemia in children: comparison between allogeneic bone marrow transplantation and conventional chemotherapy. Spanish Working Party for BMT in Children (GETMON)

BACKGROUND AND OBJECTIVE

To compare the estimated survival and disease-free survival between children with Ph1-positive chronic myeloid leukemia treated with allogeneic bone marrow transplantation or conventional chemotherapy.

DESIGN AND METHODS

In this retrospective study we compared the results obtained in a group of 14 children who received allogeneic bone marrow transplantation (BMT) between 1983 and 1993, and another group of 27 children treated with busulfan, hydroxyurea or alpha-interferon during the same time period. Patients were transplanted at a median of 7 months from diagnosis and all except one were in their first chronic phase. Conditioning consisted in total body irradiation and cyclophosphamide in 12 cases, and busulfan was added in two.

RESULTS

Of the 14 patients treated with BMT, two died of transplant-related complications and two relapsed 18 and 48 months after the BMT. Ten children remain alive and disease free at a median follow up of 60 months. The probability of DFS at 5 years is 70%. Of the 27 patients treated with chemotherapy, 22 have died at a median of 36 months from diagnosis. The probability of survival at 5 years is 5% versus 83% for the BMT group (p = 0.001).

INTERPRETATION AND CONCLUSIONS

Allogeneic BMT is a safe and very effective treatment for Ph-positive CML in children. Patients who have an HLA-identical sibling donor must receive a transplant as soon as possible after being diagnosed.

Comparative study of two non-steroidal anti-inflammatory eyedrops, 0.1% indomethacin versus 0.1% diclofenac in pain control post photorefractive keratectomy

We evaluated the efficacy and safety of 0.1% indomethacin and 0.1% diclofenac solutions, in controlling pain post excimer laser photorefractive keratectomy (PRK). After written consent, 61 informed patients (23 males, 38 females; mean age = 33.5 +/- 8.4 yrs) were enrolled in a double-masked, randomized, comparative study and assigned to either indomethacin or diclofenac treatment. Subjective preoperative evaluation of individual susceptibility to pain evoked by topical application of 1% tetracaine vs saline served as reference for further post-operative pain measurement using a visual analog rating scale. Ocular and cephalic pain, itching, foreign body sensation, insomnia, photophobia, blepharospasm as well as systemic analgesic medication and alcohol intake were monitored for 3 days following photoablation as well as the re-epithelialization process. Both solutions significantly reduced pain on the first day following excimer laser PRK, and this activity was maintained until the end of the observation period. At Day 0 the first measure of pain level was slightly higher in the indomethacin group (p < 0.05) and could be related to a possible anaesthetic effect of Diclofenac. During the follow-up the oral intake of analgesics was higher in the diclofenac group, however this difference was not significant. Wound healing rate was not affected by indomethacin or diclofenac administration. These data suggest that both 0.1% indomethacin and 0.1% diclofenac ophthalmic solutions may help to control the pain induced by excimer laser PRK without any deleterious effect on corneal wound healing.

Effects of catecholamines on the pulmonary venous bed in sheep

OBJECTIVE

To assess the effects of various catecholaminergic agents on pulmonary venous tone.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Physiology laboratory of a university hospital.

SUBJECTS

Thirty anesthetized, mechanically ventilated adult sheep.

INTERVENTIONS

Four groups of six animals received 1-hr infusions of norepinephrine (0.5 microg/kg/min), epinephrine (0.5 microg/kg/ min), dopamine (10 microg/kg/min), or dobutamine (10 microg/kg/min).

MEASUREMENTS AND MAIN RESULTS

A 7-Fr pulmonary artery catheter was placed in a proximal location to measure cardiac output and pressure in a large pulmonary vein (Ppw) after balloon inflation. Another catheter wedged in a small pulmonary artery measured pressure in a small pulmonary vein (Pdw). A third catheter measured left atrial pressure (PLA ). This method was able to detect the pulmonary venoconstrictive effects of histamine in a separate group of six animals. Pdw-PLA increased from a mean of 2.0+/-1.7 to 3.0+/-1.5 (SD) cm H2O (p < .01), 2.3+/-1.6 to 4.4+/-1.3 cm H2O (p < .01), and 1.7+/-1.0 to 3.5+/-2.2 cm H2O (p < .05) with norepinephrine, epinephrine, and dopamine, respectively. All of these drugs increased Pdw-Ppw, but only norepinephrine and epinephrine increased Ppw-PLA . No change in either pressure difference was observed with dobutamine. Elevation of cardiac output alone could not account for these findings since the increase in cardiac output induced by fluid infusion did not change the pressure differences.

CONCLUSION

Norepinephrine, epinephrine, and dopamine at doses commonly used in humans increase pulmonary venous tone in sheep.

Purification and determination of the action pattern of Haliotis tuberculata laminarinase

The major laminarinase activity (EC 3.2.1.39) from the gastropodean marine mollusc Haliotis tuberculata was purified to homogeneity by cation exchange chromatography and its action pattern was investigated by HPAEC-PAD analysis of the degradation of various laminarin samples. It consists of a 60 kDa protein capable of depolymerizing the unbranched portions of the beta-(1-->3), beta-(1-->6)-glucan, down to laminaritriose. The enzyme operates via a molecular mechanism retaining the anomeric configuration. As the purified protein does not cleave the beta-(1-->6) linkages, it can be used for the structural analysis of laminarins.

[Prognostic factors in low-grade lymphoma]

PURPOSE

Prognostic factors in low grade non-Hodgkin's lymphoma (LGL) are not well established. The aim of this study is to investigate prognostic factors on LGL treated in our institution during the last decade.

PATIENTS AND METHODS

The study was carried out on 70 cases of newly diagnosed LGL, most treated with CVP or clorambucil and prednisone. The median follow-up was 37 months (1-132). Variables reported as prognostic factors in previous series were subjected to bivariate and multivariate analysis.

RESULTS

Relevant clinical features were: Ann Arbor III-IV stage 74%, ECOG > or = 2-17%, bone marrow involvement 60% and large tumor burden according to MD Anderson criteria 21%. Complete response (CR) was achieved in 50% and partial response in 29%. In bivariate analysis factors related with poor CR were B symptoms, large tumor burden, high LDH and more than one extranodal site involvement. Logistic regression showed that large tumor burden (p = 0.02; OR = 0.07) and B symptoms (p = 0.07; OR = 0.14) were the best prognostic factors of poor CR. Five year global survival (GS) was 55%, with a median of 76 months. In univariate analysis factors related with GS were ECOG > or = 2, B symptoms, bulky, large tumor burden, retroperitoneo involvement and absence of CR. In multivariate analysis the only factor related with poor GS was large tumor burden (p < 0.00001; RR = 5.93). When therapeutic response was included in the model, absence of CR (p = 0.008; RR = 3.40) and large tumour burden (p = 0.005; RR = 3.86) were the factors selected.

CONCLUSIONS

In LGL tumor burden was the most important prognostic variable. Tumor response showed less importance than in high grade lymphomas.

Joint time and time-frequency optimal detection of K-complexes in sleep EEG

Automated detection of waveforms such as delta and K-complex in the EEG is an important component of sleep stage monitoring. The K-complex is a key feature that contributes to sleep stages assessment. However, its automated detection is still difficult due to the stochastic nature of the EEG. In this paper, we propose a detection structure which can be interpreted as joint linear filtering operations in time and time-frequency domains. We also introduce a method of obtaining the optimum detector from training data, and we show that the resulting receiver offers better performances than the one obtained via the Fisher criterion maximization. The efficiency of this approach for K-complexes detector design is explored. It results from this study that the obtained receiver is potentially the best one which can be found in the literature. Finally, it is emphasized that this methodology can be advantageously used to solve many other detection problems.

Value of the venous-arterial PCO2 gradient to reflect the oxygen supply to demand in humans: effects of dobutamine

OBJECTIVE

To test the value of venous-arterial PCO2 gradient (deltaPCO2) measurements to reflect the adequacy of cardiac index (CI) to oxygen demand in patients submitted to rapid changes of CI and oxygen demand.

DESIGN

Prospective, comparative study.

SETTING

Medical intensive care unit of a university hospital.

PATIENTS

Ten patients with congestive heart failure exhibiting low baseline CI (< or =2.5 L/min/m2) but no evidence of global tissue hypoxia, as attested by the absence of clinical signs of shock and by normal blood lactate concentrations.

INTERVENTIONS

Infusion of incremental doses of dobutamine: 0 (D0), 5 (D5), 10 (D10), and 15 (D15) microg/kg/min.

MEASUREMENTS AND MAIN RESULTS

The CI increased by a linear fashion from D0 (1.6+/-0.1 L/min/m2) to D15 (2.4+/-0.2 L/min/m2) (p< .05). The mixed venous oxygen saturation (SVO2) increased from D0 (49+/-2%) to D10 (61+/-2%) (p < .05) and remained unchanged from D10 to D15 (60+/-2%). The oxygen extraction ratio (O2 ER) and the deltaPCO2 decreased from D0 (48+/-2% and 9+/-1 torr [1.2+/-0.3 kPa], respectively) to D10 (36+/-2% and 5+/-1 torr [0.7+/-0.1 kPa], respectively) (p < .05 for both comparisons) and remained unchanged from D10 to D15 (36+/-2% and 6+/-1 torr [0.8+/-0.1 kPa], respectively). The biphasic courses of SVO2, O2 ER, and deltaPCO2 were related to the course of oxygen consumption that remained constant from D0 (113+/-9 mL/min/m2) to D10 (112+/-8 mL/min/m2) and significantly increased from D10 to D15 (127+/-10 mL/min/m2) (p <.05).

CONCLUSIONS

deltaPCO2 can be reliably used at the bedside for informing on the adequacy of CI with respect to a given metabolic condition, and particularly for detecting changes in oxygen demand (e.g., the changes accompanying drug-induced changes in CI). In this regard, deltaPCO2, together with O2 ER and SVO2, can help to assess the adequacy of CI to global oxygen demand.

Quality of life in young adults having received a BMT during childhood: a GETMON study. Grupo Español de Trasplante de Médula Osea en el Niño

A quality-of-life questionnaire study was administered in a group of 98 disease-free survivors more than 3 years after BMT. All participants were over the age of 17 years at the time of the survey. The transplants were performed between 1981 and 1993 in eight Spanish hospitals. Eighty-three percent of patients had undergone BMT for neoplastic disease. Seventy-three per cent received an allogeneic bone marrow transplantation. A modified version of a questionnaire applied in Stanford Hospital to evaluate quality of life in adults after BMT was used. A single investigator was responsible for interviewing all subjects by telephone. We compare these results with the same questionnaire applied in a control group of 58 healthy subjects of similar age. The most significant results were: BMT patients valued their quality of life more highly than the control group. The mean score for global quality of life was 8.19+/-0.17 in BMT group as compared to 7.54+/-0.13 in control group (P=0.0013). Studies were cited as the major concern in both groups: 24% in BMT group and in 69% in control group (C.I. 95%=0.59 to 0.30). The patients in the BMT group considered they had fewer problems in comparison with the control group regarding interpersonal relationships with family members and friends, sleep, depression and leisure possibilities. However, they considered they had more problems concerning their physical appearance, studies and work possibilities than their peers. Considerations regarding weight, height, sexual functioning, anxiety, tendency to suffer illness and problems with insurance were similar in both groups.

Expression of Bcl-x in erythroid precursors from patients with polycythemia vera

BACKGROUND

Deregulating the expression of Bcl-xL, an inhibitor of apoptosis, in an erythropoietin-dependent erythroblast cell line averts apoptosis induced by the withdrawal of erythropoietin. Since in polycythemia vera an abnormal clone of erythroid progenitors is independent of erythropoietin, we investigated whether the endogenous expression of Bcl-xL was deregulated in these cells.

METHODS

Erythroid colonies from patients with polycythemia vera and normal subjects were cultured in the presence and absence of erythropoietin and assessed by immunocytochemical and flow-cytometric analysis with anti-Bcl-x antibodies that recognize the two species of Bcl-x (Bcl-xL and Bcl-xS). Reverse-transcriptase-polymerase-chain-reaction analysis was used to determine which one of the two species was responsible for anti-Bcl-x staining. Bone marrow mononuclear cells from 8 healthy bone marrow donors, 14 patients with polycythemia vera, 19 patients with other myeloproliferative syndromes, and 12 patients with secondary erythrocytosis were analyzed by flow cytometry with antibodies against Bcl-x and glycophorin A, an erythroid marker.

RESULTS

Erythroid cells from patients with polycythemia vera survived in vitro without erythropoietin, and this finding correlated with the expression of Bcl-x protein (Bcl-xL messenger RNA was the main species of Bcl-x found), even in mature erythroblasts that normally do not express Bcl-x. The mean (+/-SD) percentage of cells positive for both glycophorin A and Bcl-x in the 14 patients with polycythemia vera (21.8+/-3.6 percent) was significantly higher than that in 8 normal donors (6.62+/-1.58 percent), 12 patients with secondary erythrocytosis (6.87+/-1.95 percent), 9 patients with essential thrombocythemia (3.81+/-0.97 percent), and 10 patients with chronic myeloid leukemia (2.7+/-0.41 percent).

CONCLUSIONS

Deregulated expression of Bcl-x may contribute to the erythropoietin-independent survival of erythroid-lineage cells in polycythemia vera and thereby contribute to the pathogenesis of this disease.

Characterization of a murine monoclonal antibody specific for swine beta1 integrin

Murine monoclonal antibodies were raised against porcine platelets in order to provide tools for investigating interactions of human blood cells and natural antibodies with porcine tissues. Hybridomas were screened by cellular ELISA on porcine platelets and endothelial cells. Positive clones were tested by flow cytometry for reactivity with isolated endothelial cells. One clone, NaM160-1A3, produced an antibody that stained porcine but not human endothelial cells and lymphocytes. The antibody bound to a 116 kDa glycoprotein on Western blot of both platelets and endothelial cells. The antigen was purified from a platelet lysate by affinity chromatography, first on a ConA column and then on a column presenting the immobilized NaM160-1A3 antibody. Two glycoproteins were obtained: one (116 kDa) was recognized by the antibody and one (150 kDa) was not. The 116 kDa protein had an internal decapeptide identical with human beta 1 integrin, and the 150 kDa protein had an internal amino acid sequence belonging to porcine alpha 2 integrin. Therefore, the NaM160-1A3 antibody was directed against porcine beta 1 integrin and allowed the purification of the complex alpha 2 beta 1, also termed Very Late Antigen 2 (VLA-2). It did not recognize human beta 1 integrin.

Pneumococcal pericarditis with cardiac tamponade in a patient with chronic graft-versus-host disease

We report a case of pneumococcal pericarditis in a 13-year-old boy following allogeneic BMT from an HLA-identical unrelated donor. The post-transplant course was complicated by chronic GVHD which led to reinstitution of immunosuppressive therapy. Eight months after BMT the patient developed pericarditis with cardiac tamponade, and Streptococcus pneumoniae was isolated in the pericardiocentesis fluid. This is the first reported case of pneumococcal pericarditis after BMT. Although pericardial effusions after allogeneic BMT are often sterile and related to conditioning therapy or associated with chronic GVHD, rapid microbiological investigation and empirical treatment with antibiotics are necessary. Prophylaxis for pneumococcal infection in patients with chronic GVHD is recommended.

Pathogenesis of polycythemia vera

BACKGROUND AND OBJECTIVE

Polycythemia vera (PV) is an acquired clonal myeloproliferative disorder characterized by increased production of mature red cells. We still lack a molecular target responsible for this disorder; however, recent investigations have focused on a number of molecules involved in signal transduction pathways mediated by erythropoietin (Epo) and other growth factors. Here we review the implication of these molecules in the pathogenesis of PV.

INFORMATION SOURCES

The material reviewed in this work includes articles published in journals covered by Medline. We also include data obtained in our laboratory regarding to the significance of apoptosis inhibitory proteins in erythroid development.

STATE OF THE ART AND PERSPECTIVES

Overproduction of erythroid cells in PV is particular in that it occurs in the absence of a recognizable physiologic stimulus, since circulating serum levels of Epo are normal or lower than normal. Genetic analysis as well as in vitro studies, have established an essential role for Epo in the survival and maturation of committed erythroid progenitors. Epo initiates its cellular response by binding to the Epo receptor (EpoR) expressed on the surface of immature erythroblasts. Following ligand binding, EpoR is known to activate a cytoplasmic protein tyrosine kinase, Jak2 which triggers a signal transduction cascade that leads to the development of early erythroid progenitors into mature erythroblast cells. Although the mechanism underlying the increased erythroid production in PV is not well understood, a number of causes have recently came for which may provide insights not only for the pathogenesis of PV but also for a fundamental biological process: the mechanism whereby a multipotential stem cell gives rise to a particular cell lineage.