Red blood cell regeneration induced by subcutaneous recombinant erythropoietin: iron-deficient erythropoiesis in iron-replete subjects [see comments]

Limited red blood cell (RBC) regeneration often prevents collection of sufficient blood from autologous donors. We studied the effects of subcutaneous recombinant erythropoietin (rEPO) in subjects making frequent blood donations. Six healthy iron-replete male subjects took rEPO (200 U/kg) subcutaneously daily, and donated blood (450 mL) twice a week for 3 weeks. During a control study, these subjects also attempted twice-weekly blood donations without rEPO. Four other males given rEPO, including one with idiopathic hemochromatosis, waited until day 8 to begin blood donations. All healthy subjects took oral ferrous sulfate. Subcutaneous rEPO given with blood donations resulted in a marked reticulocytosis (mean peak value 568 +/- 159 x 10(9)/L v 235 +/- 77 x 10(9)/L, control study; P < .05), and enhanced RBC production at 28 days (1,208 +/- 227 mL v 719 +/- 161 mL, P < .05). rEPO in advance of blood donations was slightly less effective in normal subjects (941 +/- 139 mL, P < .05); however, the subject with hemochromatosis produced substantially more RBCs (1,764 mL) than any normal subject. rEPO-treated normal subjects (but not the rEPO-treated patient with hemochromatosis or untreated controls) produced iron-deficient RBCs with elevated zinc protoporphyrin levels and low hemoglobin content. These cells appeared within 1 week of rEPO administration and before laboratory confirmation of depleted iron stores. Thus, subcutaneous rEPO is an effective stimulant of erythropoiesis in nonanemic blood donors. However, in addition to eventual depletion of iron stores, early functional iron deficiency affects response to the drug.     

Beta 2-integrin and L-selectin are obligatory receptors in neutrophil aggregation [see comments]

We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to beta 2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and beta 2- integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the beta 2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an approximately 50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by approximately 50%. We examined the aggregation of neutrophils from patients genetically deficient in beta 2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and beta 2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the beta 2-integrin and the other expressed the L- selectin adhesive epitope.     

Expression of specific granule markers on the cell surface of neutrophil cytoplasts

The widespread assumption that cytoplasts generated from human polymorphonuclear leukocytes (PMNs) are vesicles consisting solely of cytoplasm surrounded by plasma membrane and devoid of granule activity remains to be tested. PMN cytoplasts were prepared by centrifugation of intact cells on a Ficoll step gradient in the presence of cytochalasin B. Two granule membrane markers, Mol, a fluorometrically detectable antigen, and cytochrome b, both of which have been shown to translocate to the plasma membrane during granule release, were compared for their activity in cytoplasts and intact PMNs. We found that the amount of Mol detected on the plasma membrane of intact PMNs, as compared with other membrane markers (such as antigens LFA-1 and beta 2m), increased 1.6- fold upon exposure of PMNs to Ficoll plus cytochalasin B prior to centrifugation. Another twofold increase in Mol expression occurred upon cytoplast preparation. Release of the granule enzymes, vitamin B12- binding protein, and lysozyme were also followed and correlated well (r = .78 and .92) with the amount of Mol antigen present on the cell surface. Cytochrome b was also found to be higher (1.4-fold) on plasma membranes isolated from cytoplasts than on plasma membranes isolated from intact control cells. These results indicate that some fusion of granule membranes and plasma membranes occurred during treatment of PMNs with Ficoll plus cytochalasin b and during cytoplast preparation.     

Negative flecainide test in Brugada syndrome patients with previous positive response.

Class I antiarrhythmic drug infusion has been established as the standard test to unmask Brugada syndrome. This report presents two patients with Brugada syndrome with positive flecainide response which was not reproducible in a subsequent test.     

Seasonal variations in admissions for acute myocardial infarction. The PRIMVAC study

INTRODUCTION AND OBJECTIVES: Some authors have described seasonal variations in the incidence of acute myocardial infarction. The aim of this study was to determine the existence of seasonal rhythms in admissions for acute myocardial infarction to coronary care units, and in mortality, and to analyze the influence of age on environmental factors. PATIENTS AND METHOD: The study included a total of 8400 consecutive patients with acute myocardial infarction admitted to 12 coronary care units in the PRIMVAC registry from January 1995 to December 1999. Seasonal rhythms were analyzed with the time series method and the Cosinor regression equation. The influence of age was analyzed with the chi 2 test. RESULTS: The total number of admissions increased in winter and decreased in summer. The highest peak (acrophase) occurred in winter, with 2183 cases (r2=0.91), specifically in February, with 742 cases (r2=0.66). The age of the patients conditioned seasonal variations (P=.006), and the influence was statistically significant for patients over 65 years of age. Changes in mortality with time did not reach statistical significance. CONCLUSIONS: A seasonal rhythm in admissions for acute myocardial infarction was found, with an increase in winter and a decrease in summer. Age conditioned the effect of environmental factors on acute myocardial infarction, and patients aged 65 years or older were more sensitive to mechanisms that led to increases in admissions in winter.     

Decremental atriofascicular accessory pathway with bidirectional conduction: delineation of atrial and ventricular insertion by radiofrequency current application

A 17-year-old girl with a corrected complex congenital heart disease and recurrent episodes of supraventricular tachycardia was referred for catheter ablation. Electrophysiologic studies revealed the presence of an accessory pathway (AP) with bidirectional conduction and decremental properties. We demonstrated a course parallel to the node-His AV conduction system. Transient abolition of the bidirectional conduction through the AP was obtained by radiofrequency application to the ventricular insertion located in the distal right bundle branch and to the atrial insertion, located in the mid-anterior atrial septum. Radiofrequency application at the low anterior atrial septum, above the His bundle, successfully abolished AP conduction without affecting AV nodal conduction. Demonstration of the course and insertions of the AP, its bidirectional decremental conduction properties, and the association with a complex congenital heart disease are exceptional and interesting findings and raise the possibility of an accessory AV node with a parallel conduction pathway to the right bundle branch.     

Primary aortoenteric fistula: a rare cause of gastrointestinal bleeding in young adults

Aortoenteric fistula is defined as a communication between the native aorta and any portion of the gastrointestinal tract. Depending on previous aortic grafting it can be classified as primary, without previous grafting, or secondary. Primary aortoenteric fistula is less frequent and usually arises from an abdominal aortic aneurysm. Clinical presentation is usually gastrointestinal bleeding. The main diagnostic procedures are gastroscopy and computed tomography. We report the case of a 46-year-old man who presented to the emergency room with gastrointestinal bleeding and an abdominal pulsatile mass. Although complementary tests and clinical signs suggested a diagnosis of primary aortoenteric fistula, the communication was not observed on gastroscopy and was confirmed by exploratory laparotomy. Despite aggressive surgical treatment, the prognosis of this entity is poor.     

Effects of Ethanol on Intestinal Absorption of Drugs.

The effect of chronic alcohol intake on the intestinal absorption of seven compounds belonging to a homologous series (ciprofloxacin derivatives) was evaluated using an in situ rat gut technique that measures the intrinsic absorption rates of the compounds both in control and chronic alcohol-fed rats. For chronic alcohol treatment, the animals were fed a liquid diet containing ethanol (36% of calories), whereas an isocaloric diet was given to the pair-fed control animals. The biophysical absorption model, relating the intestinal absorption rate constants and partition indexes of the tested compounds, was then established either for control or alcohol-fed animals. Differences were analyzed and tentatively interpreted on the basis of general diffusion principles. Results revealed that, in chronic alcohol-fed animals, hydrophilic homologs are absorbed at a significantly faster rate than in control ones, whereas lipophilic homologs do not change their absorption rate relative to controls. Results demonstrate that the bulk polarity of the microvillous lipoidal membrane is enhanced by chronic ethanol intake, whereas basic features of the aqueous boundary layer are not altered. These observations suggest that the physicochemical properties of the compounds are an important factor in explaining the influence of chronic alcohol intake on passive intestinal absorption of xenobiotics. The possible practical implications of our results are discussed from a speculative viewpoint