Broadband luminescence in defect-engineered electrochemically produced porous Si/ZnO nanostructures.

The fabrication, by an all electrochemical process, of porous Si/ZnO nanostructures with engineered structural defects, leading to strong and broadband deep level emission from ZnO, is presented. Such nanostructures are fabricated by a combination of metal-assisted chemical etching of Si and direct current electrodeposition of ZnO. It makes the whole fabrication process low-cost, compatible with Complementary Metal-Oxide Semiconductor technology, scalable and easily industrialised. The photoluminescence spectra of the porous Si/ZnO nanostructures reveal a correlation between the lineshape, as well as the strength of the emission, with the morphology of the underlying porous Si, that control the induced defects in the ZnO. Appropriate fabrication conditions of the porous Si lead to exceptionally bright Gaussian-type emission that covers almost the entire visible spectrum, indicating that porous Si/ZnO nanostructures could be a cornerstone material towards white-light-emitting devices.

Chiral templating of alumina nanofilms by the atomic layer deposition process.

In this communication, we describe the synthesis of new chiral alumina nanofilms and surfaces. Our method is based on chiral templating of alumina nanofilms by cellulose microfibers using the atomic layer deposition process. The chiral nature of the alumina nanofilms was characterized by a variety of techniques, such as quartz crystal microbalance, chiral circular-dichroism adsorption, chiral high-performance liquid chromatography and cyclic voltammetry measurements.

Growth and modelling of spherical crystalline morphologies of molecular materials.

Crystalline, yet smooth, sphere-like morphologies of small molecular compounds are desirable in a wide range of applications but are very challenging to obtain using common growth techniques, where either amorphous films or faceted crystallites are the norm. Here we show solvent-free, guard flow-assisted organic vapour jet printing of non-faceted, crystalline microspheroids of archetypal small molecular materials used in organic electronic applications. We demonstrate how process parameters control the size distribution of the spheroids and propose an analytical model and a phase diagram predicting the surface morphology evolution of different molecules based on processing conditions, coupled with the thermophysical and mechanical properties of the molecules. This experimental approach opens a path for exciting applications of small molecular organic compounds in optical coatings, textured surfaces with controlled wettability, pharmaceutical and food substance printing and others, where thick organic films and particles with high surface area are needed.

Desferrioxamine (DFO) conjugated with starch decreases NAD redox potential of intact red blood cells (RBC): evidence for DFO as an extracellular inducer of oxidant stress in RBC.

Desferrioxamine (DFO) is an important iron-chelating agent. It has also been thought of as an agent with anti-oxidant potential as it chelates ferric iron in various parts of the body. However, there is evidence suggesting that it may paradoxically affect red blood cells (RBCs) by inducing intracellular oxidant stress. Recently we observed that incubation of RBCs with DFO decreases NAD redox potential in normal RBC. To further understand the mechanism of DFO's interaction with RBC, we conducted a study to determine the effect of extracellular DFO upon RBC's redox status. We examined NAD redox potential in intact RBC (N = 7) incubated with DFO conjugated to starch. RBCs were incubated with 4 mM DFO for 3(1/2) hr and with 6 mM DFO for 2 and 3(1/2) hr. Significant decreases in NAD redox potential were observed after the incubations. With 4 mM DFO at the 3 (1/2) hr time point the mean decrease was 12.37% +/- 9.96% (P < 0.0085). With 6 mM DFO, the mean decreases were 18.54% +/- 9.79% (P < 0.0013) and 19.16% +/- 8.78% (P < 0.0006) for the 2 and 3 (1/2) hr incubations, respectively. DFO by itself is very poorly permeable to RBC. Conjugation with starch further ensured impermeability of DFO. The data presented here confirm the oxidant effect of DFO on RBC. The data also demonstrate that the effect of DFO on RBC's NAD redox potential originates extracellularly.

Deferiprone, an oral iron chelator, ameliorates experimental colitis and gastric ulceration in rats.

Iron is pivotal is producing tissue-damaging reactive oxygen metabolites. Our aim is to determine the antiinflammatory activity of deferiprone, an oral iron chelator, in experimental colitis and gastritis. Colitis was induced by intraceccal administration of 2 ml 5% acetic acid or by intracolonic administration of 0.1 ml 3% iodoacetamide, with or without cotreatment with deferiprone. Gastritis was induced by intragastric administration of ethanol or hydrochloric acid (HCl) and by subcutaneous injection of indomethacin, with and without deferiprone. Rats were killed 24 hours after acetic acid and iodoacetamide, 30 minutes after ethanol, one hour after HCl, and three hours after indomethacin administration. The colon or stomach was isolated, macroscopic damage was measured, and mucosal samples were obtained for determination of eicosanoid generation, myeloperoxidase (MPO), and nitric oxide synthase (NOS) activities. Deferiprone decreased iodoacetamide and acetic acid-induced macroscopic colonic damage by 67% and 69%, respectively, and macroscopic gastric damage by 91%, 68%, and 46% induced by ethanol, HCl, and indomethacin, respectively. The effect of deferiprone was accompanied by significant decrease in colonic and gastric, MPO and NOS activities, and colonic prostaglandin E2 (PGE2) generation, in acetic acid, ethanol, and indomethacin models, whereas in the iodoacetamide and HCl models attenuation of the decrease in PGE2 generation was seen. Deferiprone is protective in experimental colitis and gastritis, probably due to decreased production of iron-dependent oxygen-free radicals. Oral iron chelators may constitute a novel approach to ameliorate gastrointestinal inflammatory disorders.

Transport of 14C-deferiprone in normal, thalassaemic and sickle red blood cells.

The transport of deferiprone (L1) in normal (N), sickle (S) and thalassaemic (T) red blood cells (RBC) was determined by incubation with 14C-L1 at 37 degrees C. Following incubation with 0.5 mM 14C-L1 for 4 h, the intracellular concentration of L1 in T RBC was 3 times higher than was found extracellularly. In contrast, no concentration gradient across N and S RBC membranes was detected. Efflux studies showed that T RBC released only 17 +/- 2% of 14C-L1 into the extracellular space. We hypothesize that L1 accumulation in T RBC results from their high content of chelatable iron and formation of large, hydrophilic L1-Fe(III) complexes trapped within the cytosol.

Deferiprone therapy in homozygous human beta-thalassemia removes erythrocyte membrane free iron and reduces KCl cotransport activity.

Deposition of free iron is a characteristic feature of beta-thalassemia (beta-thal) red blood cells believed to play an important role in the generation of oxidative injury to the cell membrane. Increased red blood cell KCI cotransport, reduced K content, and cell dehydration are also found in beta-thal red blood cells. It is not known, however, whether deposition of free iron plays a role in these membrane transport changes. To explore this issue, we studied-both in vitro and in vivo-the effect on KCI cotransport of removing red blood cell membrane free iron from beta-thal erythrocytes. Eleven patients with beta-thal major who underwent long-term transfusion and were treated with deferiprone (75 mg/kg/day) for 9 months participated in the study. Deferiprone therapy removed membrane free iron from beta-thal erythrocytes, which was followed by reduced KCI cotransport activity. The reduced KCI cotransport activity was accompanied by an increase in the red blood cell K content. These data suggest that the increased activity of KCI cotransport in beta-thal red blood cells is mediated by the deposition of membrane free iron, a mechanism that may be attenuated by deferiprone therapy.

The molecular pathobiology of cell membrane iron: the sickle red cell as a model.

The molecular pathobiology of membrane-associated iron is clearly illustrated by the sickle red blood cell. The cytosolic aspect of the membranes of these cells carries several discrete iron compartments, including denatured hemoglobin and free heme, as well as molecular iron associated with membrane aminophospholipid and denatured globin. Affinity of the membrane for molecular iron is extraordinarily high and predicted to keep cytosolic free iron concentration < 10(-20) M. Membrane iron is bioactive and able to valence cycle, thus serving as a catalyst for generation of highly reactive hydroxyl radical. As a consequence of this oxidative biochemistry at the cytosol/membrane interface, multiple membrane defects arise that are of pathophysiologic importance. Thus, sickle red cells provide a pathobiologic paradigm for the membrane-damaging effect of iron-mediated targeting of oxidative damage at a sub-cellular level. This is relevant to a variety of biologic conditions accompanied by decompartmentalization of iron.

Removal of erythrocyte membrane iron in vivo ameliorates the pathobiology of murine thalassemia.

Abnormal deposits of free iron are found on the cytoplasmic surface of red blood cell (RBC) membranes in beta-thalassemia. To test the hypothesis that this is of importance to RBC pathobiology, we administered the iron chelator deferiprone (L1) intraperitoneally to beta-thalassemic mice for 4 wk and then studied RBC survival and membrane characteristics. L1 therapy decreased membrane free iron by 50% (P = 0.04) and concomitantly improved oxidation of membrane proteins (P = 0.007), the proportion of RBC gilded with immunoglobulin (P = 0.001), RBC potassium content (P < 0.001), and mean corpuscular volume (P < 0.001). Osmotic gradient ektacytometry confirmed a trend toward improvement of RBC hydration status. As determined by clearance of RBC biotinylated in vivo, RBC survival also was significantly improved in L1-treated mice compared with controls (P = 0.007). Thus, in vivo therapy with L1 removes pathologic free iron deposits from RBC membranes in murine thalassemia, and causes improvement in membrane function and RBC survival. This result provides in vivo confirmation that abnormal membrane free iron deposits contribute to the pathobiology of thalassemic RBC.

Isolated beta-globin chains reproduce, in normal red cell membranes, the defective binding of spectrin to alpha-thalassaemic membranes.

Alpha-thalassaemic erythrocytes develop a specific membrane skeletal defect that is manifest as a loss of normal spectrin-binding sites on the inner surface of the thalassaemic membranes. To test whether this lesion could be caused by the excess free beta-globin chains that accumulate in alpha-thalassaemic red cells, we incubated normal red cell membranes with native, haem-containing alpha or beta globin chains or with haemoglobin A. Spectrin-depleted inside-out membrane vesicles (IOVs) derived from membranes incubated with beta-globin chains bound only 9 +/- 3% as much spectrin as IOVs from control membranes incubated with bovine serum albumin. In contrast. IOVs from membranes incubated with alpha-globin chains or haemoglobin A were nearly normal (79 +/- 3% and 86 +/- 5% of controls, respectively). This differential effect of globin chains was not seen when membranes were first transformed into spectrin-depleted IOVs and then incubated with the isolated globin chains. Under these conditions, both alpha and beta globin chains reduced the spectrin-binding capacity of the IOVs by approximately 45% (alpha 46 +/- 7%, beta 43 +/- 6%) whereas haemoglobin A had no effect. Unlike IOVs, spectrin isolated from membranes exposed to alpha or beta globin chains bound normally to IOVs and to actin (in the presence of protein 4.1). These studies show that isolated beta-globin chains (but not alpha-globin chains) can produce a spectrin-binding defect in normal red cell membranes similar to that seen in alpha thalassaemia. The existence of similar defects in the membrane skeletons of red cells from other diseases with unstable beta globins suggests a common pathophysiology for the premature destruction of these cells.

Extremely high avidity association of Fe(III) with the sickle red cell membrane.

Red blood cells (RBCs) from patients with sickle cell anemia and thalassemia carry abnormal accumulations of molecular Fe(III) at the cytosol/membrane interface. The avidity of the red cell membrane for this iron has not been defined. Using open ghost membranes prepared from sickle RBC, we examined the ability of membrane-associated Fe(III) to resist removal by 15 chelators representing a 40-log range of affinities for Fe(III). Efficacy of chelators was compared with literature values for their idealized affinity for iron as represented by the cummulative stability constant (beta n), their effective stability constant reflecting affinity under biologic conditions (Keff), and an indicator of their ability to chelate Fe(III) in the presence of an insoluble phase of iron (Ksol). Deferoxamine, a very high affinity chelator having log beta n = 30.6, was found to be the lowest affinity chelator able to remove RBC membrane Fe(III). Regardless of chelator beta n, only those agents able to preserve log Keff > or = 12 were able to do so, indicating that the membrane's effective avidity for Fe(III) is on the order of 10(12). Additional confirmation that membrane avidity for Fe(III) is extremely high is found in the observation that only chelators having log Ksol > 0 were effective. Potential physiologic iron chelators in cytoplasm of pathologic red cells are unable to prevent or reverse iron accumulation on the membrane because they do not have sufficiently high affinity for iron. These data argue that RBC membrane Fe(III) is truly pathologic.

Catalysis of soluble hemoglobin oxidation by free iron on sickle red cell membranes.

Abnormal deposition of hemichrome on the inner aspect of the sickle red cell membrane promotes premature cell demise. The steps proximate to hemichrome formation in these cells are poorly understood. To test the hypothesis that the pathologic deposits of free ferric iron located on the inner aspect of sickle cell membranes would be redox active and promote oxidation of soluble oxyhemoglobin, we incubated native versus iron-stripped sickle or normal ghost membranes with oxyhemoglobin S. We found that sickle membranes exerted an exaggerated effect on methemoglobin formation in solution, an effect completely accounted for by their abnormal content of free iron. This ability of sickle membranes to promote hemoglobin oxidation was not diminished by catalase or by presence of a high-affinity, iron-inactivating chelator that is unable to remove membrane iron. Examination of those membranes likewise revealed that their free iron content promoted deposition of additional heme-protein. These results establish that the potential redox couple formed by membrane-associated ferric iron and cytoplasmic oxyhemoglobin is promotive of hemoglobin oxidation and deposition of hemichrome on the membrane. This predicts that removal of pathologic membrane iron might help prevent the detrimental formation of methemoglobin and hemichrome in vivo, insofar as this is accelerated by transition metal.

Deferiprone (L1) chelates pathologic iron deposits from membranes of intact thalassemic and sickle red blood cells both in vitro and in vivo.

Red blood cell (RBC) membranes from patients with the thalassemic and sickle hemoglobinopathies carry abnormal deposits of iron presumed to mediate a variety of oxidative-induced membrane dysfunctions. We hypothesized that the oral iron chelator deferiprone (L1), which has an enhanced capacity to permeate cell membranes, might be useful in chelating these pathologic iron deposits from intact RBCs. We tested this hypothesis in vitro by incubating L1 with RBCs from 15 patients with thalassemia intermedia and 6 patients with sickle cell anemia. We found that removal of RBC membrane free iron by L1 increased both as a function of time of incubation and L1 concentration. Thus, increasing the time of incubation of thalassemic RBCs with 0.5 mmol/L L1 from 0.5 to 6 hours, enhanced removal of their membrane free iron from 18% +/- 9% to 96% +/- 4%. Dose-response studies showed that incubating thalassemic RBC for 2 hours with L1 concentrations ranging from 0.125 to 0.5 mmol/L resulted in removal of membrane free iron from 28% +/- 15% to 68% +/- 11%. Parallel studies with sickle RBCs showed a similar pattern in time and dose responses. Deferoxamine (DFO), on the other hand, was ineffective in chelating membrane free iron from either thalassemic or sickle RBCs regardless of dose (maximum, 0.333 mmol/L) or time of incubation (maximum, 24 hours). In vivo efficacy of L1 was shown in six thalassemic patients whose RBC membrane free iron decreased by 50% +/- 29% following a 2-week course of L1 at a daily dose of 25 mg/kg. As the dose of L1 was increased to 50 mg/kg/d (n = 5), and then to 75 mg/kg/d (n = 4), 67% +/- 14% and 79% +/- 11%, respectively, of their RBC membrane free iron was removed. L1 therapy--both in vitro and in vivo--also significantly attenuated the malondialdehyde response of thalassemic RBC membranes to in vitro stimulation with peroxide. Remarkably, the heme content of RBC membranes from L1-treated thalassemic patients decreased by 28% +/- 10% during the 3-month study period. These results indicate that L1 can remove pathologic deposits of chelatable iron from thalassemic and sickle RBC membranes, a therapeutic potential not shared by DFO. Furthermore, membrane defects possibly mediated by catalytic iron, such as lipid peroxidation and hemichrome formation, may also be alleviated, at least in part, by L1.

[A national qualifying internal medicine examination for Israeli medical students].

In 1991 the deans of the 4 medical schools in Israel decided to institute a national qualifying examination in internal medicine. This marked the beginning of the process of unifying the qualifying examinations in all major medical fields. We describe the development of the examination, experience with its administration to 720 students in 1992-1994, and the outcome of this initial effort. The examinations were prepared by a committee of senior faculty from the 4 schools, representing all the relevant clinical areas. Professional consultation was provided by the Unit for Medical Education of Tel Aviv University. Each examination consisted of 180 multiple choice items, reflecting an agreed representation of the various medical specialties, and was designed to test both comprehension and problem-solving ability. A syllabus was published by the committee and distributed to students and faculty in preparation for the examination. In composing the examination, the committee took into consideration differences in general policy and varying emphases in the curricula of the 4 schools. Analysis of the results of the 3 annual examinations showed both a high level of reliability and high quality of the majority of the individual test items. There was a trend with time to slightly lower average scores, and fewer passed the exam last year. There was improvement in the results after the first 2 years in the area of problem-solving related to interpretation of imaging, blood smears and clinical photographs, but this trend did not continue into 1994. The introduction of a high level examination based on a common syllabus provided important feedback, improving both student motivation and clinical teaching. For all schools, the outcome of the examination served as an important external indicator of teaching standards. Following this positive experience, uniform examinations in surgical subjects and pediatrics were introduced for the first time in 1993. The committee recommends that Israeli medical schools gradually introduce a comprehensive qualifying examination based on a mutually agreed list of objectives and syllabus.

Clinical relevance of gestational thrombocytopenia of < 100,000/microliters.

We identified 22 women with thrombocytopenia of < 100,000/microliters found incidentally during pregnancy and prospectively monitored their platelet count and clinical outcome for a minimum of 6 months postpartum. During the study period, four women became pregnant twice, accounting for a total of 26 pregnancies. The lowest platelet count during pregnancy was 65,600/microliters +/- 19,400 (mean +/- SD), and at delivery 84,500/microliters +/- 32,300 (P < 0.02). The thrombocytopenia was virtually asymptomatic in all patients during the pregnancy and delivery, whether vaginal or surgical. Neonatal platelet counts (n = 18) were normal (270,700/microliters +/- 69,900), and none of the newborns (n = 24) had a bleeding diathesis. Normalization of the platelet count (i.e., > 150,000/microliters) was documented in 18 patients within 1 month postpartum, in five within 3 months postpartum, and in two as late as 5 months after delivery. One woman did not recover from the thrombocytopenia and eventually developed other stigmata of an autoimmune disease. Long-term follow-up showed recurrence of thrombocytopenia in four patients: three in the context of a subsequent pregnancy and one who developed idiopathic thrombocytopenic purpura. Retrospective analysis of blood counts obtained from 12 previous pregnancies demonstrated thrombocytopenia of a similar degree to the index pregnancy. We conclude that gestational thrombocytopenia of < 100,000/microliters is clinically a benign phenomenon that can recur in subsequent pregnancies and is not accompanied by neonatal thrombocytopenia. In some cases, however, pregnancy-associated thrombocytopenia may be a manifestation of an autoimmune disease with its attendant implications for the neonate. Since the differential diagnosis between the two conditions may be difficult to establish when first encountered during pregnancy, a conservative approach emphasizing careful surveillance and guarded reassurance is justified as long as the platelet counts are > 50,000/microliters.

First trimester listeriosis with normal fetal outcome.

The case of a pregnant woman who in the 13th week of gestation presented with a non-specific influenza-like illness ultimately proven to be symptomatic of Listeria monocytogenes septicemia, is described. The patient elected to continue the pregnancy and following antibiotic therapy recovered and delivered a normal infant. At 18 months of age the child was healthy with normal psychomotor development. This case underscores the need to consider the possibility of Listeria monocytogenes septicemia at any stage of pregnancy, and suggests that early institution of antibiotic treatment may result in complete recovery of both mother and fetus.

[Glucose phosphate isomerase deficiency with congenital nonspherocytic hemolytic anemia].

Glucose phosphate isomerase (GPI) deficiency is an unusual cause of hereditary nonspherocytic hemolytic anemia described in Israel in 2 families of Arab ancestry. The disease, inherited as an autosomal recessive disorder, manifests itself by symptoms and signs of chronic hemolysis which are often ameliorated by splenectomy. A variety of defective GPI variants, characterized by modified physicochemical and/or kinetic properties of the enzyme have been reported, suggesting extensive polymorphism for this enzyme deficiency. We recently diagnosed GPI deficiency in a 23-year-old Jewish Ashkenazi man. Since the age of 1 year, when a diagnosis of hemolytic anemia of undetermined etiology was made, he has required frequent blood transfusion. Since splenectomy, performed when he was 6 years old, the requirement for blood transfusions diminished drastically, restricted to hemolytic crises following intercurrent febrile illnesses. To the best of our knowledge, this is the first report of GPI deficiency in an Israeli family of Ashkenazi-Russian origin.

Combined spectrin and ankyrin deficiency is common in autosomal dominant hereditary spherocytosis.

The common autosomal dominant form of hereditary spherocytosis (HS) has been genetically linked to defects of the erythroid ankyrin gene in a few families; however, the frequency of ankyrin deficiency and its relationship to red blood cell (RBC) spectrin content are unknown. To test these questions, we measured RBC spectrin and ankyrin by radioimmunoassay in 39 patients from 20 families with dominant HS. Normal RBCs contained 242,000 +/- 20,500 spectrin heterodimers and 124,500 +/- 11,000 ankyrins per cell. In dominant HS, RBC spectrin and ankyrin ranged from about 40% to 100% of normal and were continuously distributed. Measurements in the same patient on different occasions were reproducible (+/- 5% to 10%) and RBCs from affected members of a kindred contained similar amounts of spectrin and ankyrin (+/- 3% to 4%). Spectrin and ankyrin levels were almost always less than the assay controls, but were less than the normal range in only 75% and 80% of kindreds, respectively. Remarkably, the degree of RBC spectrin and ankyrin deficiency was very similar in 19 of 20 HS kindreds. One otherwise typical family differed, with marked ankyrin deficiency (45% of control) and a relatively mild spectrin deficit (81%). We conclude that most patients with dominant HS have combined ankyrin and spectrin deficiency and that the two proteins are usually about equally deficient, suggesting that defects in ankyrin expression, ankyrin stability, or ankyrin band 3 (AE1) interactions may be common in dominant HS.

Nonrandom association of free iron with membranes of sickle and beta-thalassemic erythrocytes.

To further define the nature of abnormal iron deposits on the membranes of pathologic red blood cells, we have used sickle cell anemia (HbSS), HbSC, and beta-thalassemic erythrocytes (RBCs) to prepare inside-out membranes (IOM) and insoluble membrane aggregates (AGGs) containing coclustered hemichrome and band 3. Study of IOM from HbSC and thalassemic patients showed that amounts of heme iron and, especially, free iron were much higher in patients who had undergone surgical splenectomy. The membrane AGGs from HbSS and beta-thalassemic RBCs contained much more globin than heme, with this discrepancy being variable from patient to patient. Although these AGGs were enriched (compared with the ghosts from which they were derived) for heme, as expected, less than 10% of total ghost heme was recovered in them. Remarkably, these AGGs also were enriched for nonheme iron, markedly so in some patients. Iron binding studies showed that the association of free iron with these hemichrome/band 3 AGGs is explained by the fact that free iron binds to denatured hemoglobin. These results document that free iron is nonrandomly associated with the membranes of sickle and beta-thalassemic RBCs. Whether this plays a causative role in the premature removal of such cells from the circulation remains to be seen.