Solubility study and intensification of extraction of phenolic and anthocyanin compounds from Oryza sativa L. 'Violet Nori'

Oryza sativa L. 'Violet Nori' is an Italian cultivar of spontaneous growing aromatic purple rice which is particularly rich in polyphenolic compounds, especially anthocyanins, conferring it an excellent antioxidant capacity. The present study aimed at increasing the extraction yields of its antioxidant compounds with green strategies and it is divided into two steps. The first step concerned a solubility study of the targeted polyphenols in different ethanol:water mixtures by means of a theoretical prediction method, using the simulation program COSMO-RS, and the subsequently confirmation of the computational results by practical experiments. Once the best extraction mixture was identified, the second step of the work was performed, with the purpose of intensifying the extraction yield. Therefore, various innovative green extraction techniques, including ultrasound, using both the probe system and the ultrasonic bath, bead milling, microwave and accelerated solvent extractions were tested and compared to conventional maceration. Results, expressed in terms of total phenolic and total monomeric anthocyanin contents, showed that the best extracting solvent for 'Violet Nori' rice was the mixture ethanol:water (60:40 v/v), being COSMO-RS computational predictions in good correlation with the experimental results. Moreover, the most efficient techniques to extract the antioxidant compounds resulted to be both ultrasound-assisted extraction probe and bead milling, that in only 5 min got the same extractive efficiency obtained after 3 h of conventional maceration.

P675 ECHO COLOR DOPPLER EVALUATION OF SPLANCHNIC HEMODYNAMIC DURING ACUTE HEART FAILURE

BACKGROUND

Acute heart failure (AHF) seems to provoke profound derangement of abdominal hemodynamic, which causes symptoms and impacts on renal function.

METHODS

27 patients (10 F - age 78 - EF 0.39) admitted for AHF underwent cardiac and abdominal ultrasound at day 1 and 5. Arterial and venous flow within liver, spleen and kidney were recorded. Portal and Splenic Vein flow was described as continuous, pulsatile or reversed, whereas hepatic vein systolic and diastolic ratio was measured. Renal Venous Doppler Profile (VDP) was classified as: continuous, pulsatile, biphasic or monophasic. Arterial Resistive Index (RI) ≥0.7 was considered elevated.

OUTCOME

At day 1 most patients presented with some degree of deranged VDP and high RI in all examined organs. At day 5, a significant proportion of patients improved their VDP in Liver, Kidney and Spleen, while the percentage of patients with collapsing IVC did not significantly change. On the arterial side, the proportion of patients with high Hepatic RI dropped significantly.

CONCLUSIONS

Our preliminary data show that most deranged VDP in abdominal organs and Hepatic RI improve after decongestion despite a nonsignificant trend in improvement in IVC profile.

RESULTS Classification day 1 day 5 p IVC Collapsing 24% 34% ns Portal Vein Continous 22% 50% Pulsatile 72% 50% Reversed 6% 0% <.05* Hepatic Vein S/D≥1 24% 59% S/D <1 60% 28% Reversed S 16% 14% <.05* Hepatic Artery RI ≥0.7 87% 36% <.05 Splenic Vein Flat 28% 57% Pulsatile 56% 33% Reversed 16% 10% <.05* Splenic Artery RI ≥ 0.7 52% 48% ns Renal Vein Continous 11% 39% Pulsatile/Biphasic 52% 52% Monophasic 37% 9% <.05* Renal Artery RI ≥0.7 63% 65% ns * Refers to normal profile versus all other deranged profiles

P2599Echo color doppler evaluation of renal hemodynamic during acute heart failure

Background

Acute heart failure (AHF) is often accompanied by impairment in renal function. A profound derangement of normal abdominal haemodynamic is always present during this clinical phase.

Methods

14 patients (6 F – mean age 80 – mean EF 0.39) admitted for acute heart failure underwent cardiac and renal Echo Doppler examination at day 1-3-5 of Hospital stay. Parameters of arterial and venous flow within cortical right kidney were recorded. Venous Doppler Profile (VDP) was classified as: continuous (C), pulsatile (P), biphasic (B) or monophasic (M) according to the growing degree of derangement. Arterial resistive index (RI) >0.8 was considered elevated. Correlation between renal hemodynamic (and its changes) with biohumoral and echo parameters was sought.

Outcome

At day 1 VDP was M or B in 8 patients (57%) and in four (50%) of them dropped to C or P at day 5. RI was elevated in 8 patients at day 1 while only in 4 at day 5. VDP and RI were not related to EF or BNP values. One patient died before day 5, no other worsening heart failure episodes occurred. Two patients (14%) developed acute kidney injury but their VDP and RI were normal and did not change. Three patients (21%) did not improve their BNP (decrease >30%) but this was not associated with VDP or RI changes. Elevated derived pulmonary artery systolic pressure (>40 mmHg) was present in 6 out of 8 patients (75%) with M or B VDP and in all 4 patients with both elevated RI and M or B VDP.

Venous Pattern Day 1 Day 3 Day 5 Continous 2 8 5 Pulsatile 4 2 4 Biphasic 2 1 2 Monophasic 6 3 2 Arterial RI >0.8 8 6 4 BNP, pg/ml 1060±1180* 372±281* 424±213* Creatinine, mg/dl 1.4±0.6 1.5±0.6 1.3±0.6 Hb, g/dl 12.1±2.3 12.3±3.6 13.2±2.3 *p>0.05.

Conclusions

This is the first study exploring changes in renal hemodynamic by echo Doppler during AHF. With respect to previous studies among stable patients, our preliminary data shows a higher proportion of deranged renal venous and/or arterial pattern. After diuretic therapy a trend towards improvement in VDP was recorded. No clear association with other clinical and hemodynamic parameters seems evident.

Interactions between commonly used left and right ventricular function indexes in stable patients

AIM

Aim of this study was to better understand interactions between left ventricular (LV) and right ventricular (RV) systolic and diastolic function echocardiographic indexes in stable cardiovascular diseased patients and in subjects with cardiovascular risk factors.

METHODS

The study enrolled 683 stable patients who were submitted to standard transthoracic echocardiography with evaluation of left ventricular ejection fraction (LVEF) (Simpson biplane method), LV and RV systolic peak on Doppler tissue imaging (LVSys and RVSys), tricuspid annulus plane systolic excursion (TAPSE), pulmonary artery systolic pressure (PASP), and multiparameter evaluation of LV and RV diastolic function utilizing E and A peak, their ratio, E peak deceleration time, E' and A' peak on Doppler tissue imaging, their ratio, and E/E' ratio.

RESULTS

Part of the considered indexes had interactions but only LVEF and TAPSE were related to all the others (LVEF P<0.001 with all the considered parameters; TAPSE P<0.001 with all parameters except with PASP=0.003). Unexpectedly TAPSE seems to have, such as LVEF, a pivotal position among LV and RV function.

CONCLUSION

The study demonstrates the existence of interactions between LV and RV function indexes; these results may be considered as a piece of evidence in favor of heart seen as a single structure.

A high-throughput assay for the detection of Tyr-phosphorylated proteins in urine of bladder cancer patients

BACKGROUND

Bladder cancer has the peculiarity of shedding neoplastic cells and their components in urine representing a valuable opportunity to detect diagnostic markers. Using a semi-quantitative method we previously demonstrated that the levels of Tyr-phosphorylated proteins (TPPs) are highly increased in bladder cancer tissues and that soluble TPPs can also be detected in patient's urine samples. Although the preliminary evaluation showed very promising specificity and sensitivity, insufficient accuracy and very low throughput of the method halted the diagnostic evaluation of the new marker. To overcome this problem we developed a quantitative methodology with high sensitivity and accuracy to measure TPPs in urine.

METHODS

The Immobilized Metal Affinity Chromatography (IMAC) was miniaturized in a 96 well format. Luminescence, visible and infrared fluorescence antibody-based detection methods were comparatively evaluated.

RESULTS

Due to their low abundance we evidenced that both phosphoprotein enrichment step and very sensitive detection methods are required to detect TPPs in urine samples. To pursue high throughput, reproducibility and cost containment, which are required for bladder cancer screening programs, we coupled the pre-analytical IMAC procedure with high sensitive detection phases (infrared fluorescence or chemiluminescence) in an automated platform.

CONCLUSIONS

A high throughput method for measuring with high sensitivity TPP levels in urine samples is now available for large clinical trial for the establishment of the diagnostic and predictive power of TPPs as bladder cancer marker.

GENERAL SIGNIFICANCE

The new assay represents the first quantitative and high throughput method for the measurement of TPPs in urine.

A common variant upstream of the PAX6 gene influences islet function in man

AIMS/HYPOTHESIS

Impaired glucose tolerance and impaired insulin secretion have been reported in families with PAX6 mutations and it is suggested that they result from defective proinsulin processing due to lack of prohormone convertase 1/3, encoded by PCSK1. We investigated whether a common PAX6 variant would mimic these findings and explored in detail its effect on islet function in man.

METHODS

A PAX6 candidate single nucleotide polymorphism (rs685428) was associated with fasting insulin levels in the Diabetes Genetics Initiative genome-wide association study. We explored its potential association with glucose tolerance and insulin processing and secretion in three Scandinavian cohorts (N = 8,897 individuals). In addition, insulin secretion and the expression of PAX6 and transcriptional target genes were studied in human pancreatic islets.

RESULTS

rs685428 G allele carriers had lower islet mRNA expression of PAX6 (p = 0.01) and PCSK1 (p = 0.001) than AA homozygotes. The G allele was associated with increased fasting insulin (p (replication) = 0.02, p (all) = 0.0008) and HOMA-insulin resistance (p (replication) = 0.02, p (all) = 0.001) as well as a lower fasting proinsulin/insulin ratio (p (all) = 0.008) and lower fasting glucagon (p = 0.04) and gastric inhibitory peptide (GIP) (p = 0.05) concentrations. Arginine-stimulated (p = 0.02) insulin secretion was reduced in vivo, which was further reflected by a reduction of glucose- and potassium-stimulated insulin secretion (p = 0.002 and p = 0.04, respectively) in human islets in vitro.

CONCLUSIONS/INTERPRETATION

A common variant in PAX6 is associated with reduced PAX6 and PCSK1 expression in human islets and reduced insulin response, as well as decreased glucagon and GIP concentrations and decreased insulin sensitivity. These findings emphasise the central role of PAX6 in the regulation of islet function and glucose metabolism in man.

Video laparoscopic surgery: is out-of-hospital thromboprophylaxis necessary?

Despite widespread use of laparoscopic procedures, no adequate data are available to support specific recommendations for venous thromboprophylaxis in patients undergoing laparoscopic surgery. This prospective, randomized trial is the first to be designed to evaluate a regimen of out-of-hospital thromboprophylaxis after laparoscopic surgery. Consecutive patients admitted for laparoscopic surgery were considered for the study. The thromboprophylaxis regimen used for each patient was based on a risk score. Possible thromboprophylactic measures included elastic stockings and pre- and postoperative Dalteparin or early ambulation. At discharge, patients were randomly allocated either to continue Dalteparin for 1 week, or to receive no further prophylaxis. Patients judged to be at low risk were not randomized. Compression ultrasound of the leg veins was performed in all patients 4 weeks after hospital discharge. Fifty-three patients, all with acute appendicitis, were judged to be at low risk of deep vein thrombosis and were not included in the randomized study. The remaining 209 patients fell into two groups: 104 patients received postdischarge Dalteparin and 105 patients did not. The incidence of deep vein thrombosis was 0% (0 of 104) vs. 0.95% (one of 105), respectively (P = 1.00). The risk of postdischarge venous thromboembolism is low in patients undergoing laparoscopic surgery who receive in-hospital thromboprophylaxis. Given this low risk, a clinical trial powered to determine if extending prophylaxis in such patients reduces the risk of clinically apparent deep vein thrombosis would be unfeasibly large.

Detection of Circulating Prostate Cancer Cells Using Real Time Rt – Pcr: Our Experience

PCR (Polymerase Chain Reaction) has revolutionized molecular genetics and continues to be applied to many fields of medicine and biology. We used nested real time RT – PCR to detect circulating prostate cells in patients affected by prostate cancer, in order to evaluate a possible clinical role of this technique. We present our initial experience.

Acute haemolysis in childhood falciparum malaria

Acute haemolysis associated with clinical episodes of high-level Plasmodium falciparum parasitaemia was studied in 20 children from an holoendemic area (coastal Tanzania). The change in blood haemoglobin (Hb) concentration ranged from -46 to g/L during the 72-h observation period and was linearly related to maximum parasitaemia. Balance studies between loss of blood Hb, increase in plasma Hb and appearance of Hb in the urine indicated that extravascular clearance of red cells was the predominant mode of erythrocyte clearance. Most subjects, however, showed minor signs of intravascular haemolysis. The plasma Hb was << 1% of blood Hb and haemoglobinuria was detected in 14/20 children but the excretion of Hb in urine was < 0.5% of total Hb loss. Haemoglobinuria was, however, a marker of severe haemolysis, since the maximum blood Hb loss in children without haemoglobinuria was 10 g/L. Erythrocyte-bound opsonins known to induce erythrophagocytosis, i.e., complement C3c fragments and autologous IgG, were increased in all patients. In the patients with major haemolysis, the changes correlated to the haemolysis over time. Hence, a similar mechanism for predominantly extravascular erythrocyte clearance may be operative in acute malarial anaemia, normal erythrocyte senescence and other forms of acute haemolysis.

K-Cl cotransport modulation by intracellular Mg in erythrocytes from mice bred for low and high Mg levels

Mg is an important determinant of erythrocyte cation transport system(s) activity. We investigated cation transport in erythrocytes from mice bred for high (MGH) and low (MGL) Mg levels in erythrocytes and plasma. We found that K-Cl cotransport activity was higher in MGL than in MGH erythrocytes, and this could explain their higher mean corpuscular hemoglobin concentration, median density, and reduced cell K content. Although mouse KCC1 protein abundance was comparable in MGL and MGH erythrocytes, activities of Src family tyrosine kinases were higher in MGH than in MGL erythrocytes. In contrast, protein phosphatase (PP) isoform 1 alpha (PP1 alpha) enzymatic activity, which has been suggested to play a positive regulatory role in K-Cl cotransport, was lower in MGH than in MGL erythrocytes. Additionally, we found that the Src family kinase c-Fgr tyrosine phosphorylates PP1 alpha in vitro. These findings suggest that in vivo downregulation of K-Cl cotransport activity by Mg is mediated by enhanced Src family kinase activity, leading to inhibition of the K-Cl cotransport stimulator PP1.

Growth of Plasmodium falciparum induces stage-dependent haemichrome formation, oxidative aggregation of band 3, membrane deposition of complement and antibodies, and phagocytosis of parasitized erythrocytes

Plasmodium falciparum-parasitized erythrocytes (RBCs) are progressively transformed into non-self cells, phagocytosed by human monocytes. Haemichromes, aggregated band 3 (Bd3) and membrane-bound complement fragment C3c and IgG were assayed in serum-opsonized stage-separated parasitized RBCs. All parameters progressed from control to rings to trophozoites to schizonts: haemichromes, nil; 0.64 +/- 0.12; 5.6 +/- 1.91; 8.4 +/- 2.8 (nmol/ml membrane); Bd3, 1 +/- 0.1; 4.3 +/- 1.5; 23 +/- 5; 25 +/- 6 (percentage aggregated); C3c, 31 +/- 11; 223 +/- 86; 446 +/- 157; 620 +/- 120 (mOD405/min/ml membrane); IgG, 35 +/- 12; 65 +/- 23; 436 +/- 127; 590 +/- 196 (mOD405/min/ml membrane). All increments in rings versus controls and in trophozoites versus rings were highly significant. Parasite development in the presence of 100 micromol/l beta-mercaptoethanol largely reverted haemichrome formation, Bd3 aggregation, C3c and IgG deposition and phagocytosis. Membrane proteins extracted by detergent C12E8 were separated on Sepharose CL-6B. Haemichromes, C3c and IgG were present exclusively in the high-molecular-weight fractions together with approximately 30% of Bd3, indicating the oxidative formation of immunogenic Bd3 aggregates. Immunoblots of separated membrane proteins with anti-Bd3 antibodies confirmed Bd3 aggregates that, in part, did not enter the gel. Immunoprecipitated antibodies eluted from trophozoites reacted preferentially with aggregated Bd3. Changes in parasitized RBC membranes and induction of phagocytosis were similar to oxidatively damaged, senescent or thalassaemic RBC, indicating that parasite-induced oxidative modifications of Bd3 were per se sufficient to induce and enhance phagocytosis of malaria-parasitized RBC.

A pre-existing infection by Mycobacterium avium subsp. avium modulates anti-Cryptococcus neoformans and anti-Candida albicans activities in human macrophages

Mycobacterium avium is a facultative intracellular microorganism, able to survive and multiply within mammalian macrophages by circumventing antimicrobial mechanisms. In this study we hypothesize that pre-existing M. avium infection could result in macrophage superinfections by other microorganisms. We found that 24 h after ingestion of M. avium at a low multiplicity of infection, macrophages are unable to efficiently produce superoxide anions when over-stimulated with phorbol esters, and that the generation of oxidative burst is only partially restored 72 h after bacteria ingestion. We also demonstrate that intracellular killing of Cryptococcus neoformans is markedly impaired in human macrophages that have previously ingested M. avium (but not other bacteria such as Escherichia coli). This inhibitory effect is observed with live mycobacteria, but not when heat-inactivated bacteria are ingested. In contrast, when Candida albicans is given to macrophages instead of C. neoformans, an enhancement of intracellular killing is observed, suggesting that cytocidal mechanisms other than respiratory burst are involved in the anti- Candidacidal activity of macrophages.

Helicobacter pylori seroprevalence in cirrhotic patients with hepatitis B virus infection

Liver cirrhosis is a significant cause of death in Italy and one of the most frequent causes of hospitalization. The burden of cirrhotic patients on the National Health System is extremely high due to the frequent need for medical care. Acute peptic ulcer and upper gastrointestinal bleeding reportedly occur in over one-third of cirrhotic patients. Since Helicobacter pylori (H. pylori) infection strongly correlates with peptic ulcer, we wished to ascertain the prevalence of H. pylori infection in cirrhotic patients. In a case-control study we looked for this infection in 45 consecutive male patients suffering from hepatitis B virus (HBV)-related cirrhosis and 310 sex and age matched blood donors resident in the same area. Antibodies against H. pylori were present in 40/45 (89%) patients and 183/310 (59%) blood donors (P<0.001). This very high prevalence of H. pylori may explain the frequent occurrence of gastroduodenal ulcer in cirrhotic patients. (See Editorial p. 203)

[Ultrasonography-guided percutaneous alcohol injection for hepatocellular carcinoma in the cirrhotic patient]

The present study, performed in the Department of Internal Medicine and Gastroenterology of Policlinico of Modena, shows the results of the treatment with percutaneous ethanol injection of cirrhotic patients with hepatocellular carcinoma. In the period between June 1991-May 1998, 37 nodules of hepatocellular carcinoma, in 26 cirrhotic patients, were treated with ethanol injection under the ecographic guidance; the total number of sessions was 179. Ten lesions were recurrences (local or distant) in patients already treated. These patients were excluded from surgical treatment because of the high age, the high surgical risk or patient's choice. "Therapeutic success", defined as radiologic (TC or RM) demonstration of complete necrosis at the end of the first cycle of treatment, was achieved in 22/27 nodules after the first treatment (81.5%). Therapeutic success of the recurrence (second treatment) was achieved in 7/10 nodules (70%). In treated patients, survival probability (obtained with Kaplan Meier method) was 84.5%, 73.0%, 50.0%, 38.5%, 26.9%, respectively at 1st, 2nd, 3rd, 4th and 5th year. After a total number of 179 sessions, there were no relevant complications. The results obtained in our experience prove the efficacy and safety of this therapeutic technique in patients with cirrhosis and hepatocellular carcinoma.

Hemolytic anemia induced by ribavirin therapy in patients with chronic hepatitis C virus infection: role of membrane oxidative damage

The antiviral drug ribavirin (RBV) is widely used in combination with interferon (IFN) in the treatment of chronic hepatitis C virus (HCV) infection. A major side effect of RBV is a reversible hemolytic anemia. We have evaluated the in vitro effects of RBV on erythrocyte adenosine triphosphate (ATP) content and on hexosemonophosphate shunt (HMS). The ATP levels were significantly decreased in the presence of RBV and the HMS was increased, suggesting the presence of red cell susceptibility to oxidation. In vivo, we have studied the hematologic effects of treatment with RBV alone or in combination with IFN in 11 patients with chronic hepatitis C: 6 were treated with RBV (1,000-1,200 mg/d) and 5 were treated with a combination of RBV and IFN (5 million U thrice weekly). Patients were studied at semi-monthly intervals from 0 to day 60 of therapy. Both treatments were associated with a significant reduction in hemoglobin levels (steady state level at day 45) and a marked increase in absolute reticulocyte counts. Erythrocyte Na-K pump activity was significantly diminished, whereas K-Cl cotransport and its dithiotreitol-sensitive fraction, malondialdehyde and methemoglobin levels were significantly increased. RBV-treated patients showed an increase in aggregated band 3, which was associated with a significantly increased binding of autologous antibodies and complement C3 fragments indicating an erithrophagocytic removal by reticuloendothelial system.

Helicobacter infection and cirrhosis in hepatitis C virus carriage: is it an innocent bystander or a troublemaker?

Since it has been shown that Helicobacter hepaticus causes both chronic hepatitis and hepatocellular carcinoma (HCC) in mice, it is suggested that differences in the progression of chronic hepatitis C may be due to a cofactor stemming from co-infection by bacteria, especially Helicobacter pylori, and/or other Helicobacter species. An assessment was made of the prevalence of H. pylori infection in HCV-positive cirrhotic patients. The presence of Helicobacter species (spp). was evaluated in resected liver tissue from HCC patients. Serum anti-H. pylori IgG antibodies were determined in 70 males with a clinical and/or histological diagnosis of cirrhosis and HCV infection and in 310 age-matched male blood donors. The prevalences of H. pylori antibody were 77% (54/70) and 59% (183/310) (P 0.004). Primers identifying 26 Helicobacter species were used to determine the presence of the genomic 16S rRNA of this genus in liver tissue resected from 25 cirrhotic HCC patients. Genomic sequences corresponding to H. pylori and H. pullorum were identified in 23 of these 25 livers. Together, these findings support the proposal that H. pylori is implicated in the pathogenesis and progression of cirrhosis, particularly in HCV-infected individuals. Involvement of Helicobacter spp. in HCC also seems highly possible.

Human immune cells as space travelers

Experiments in space have shown that T lymphocyte function is altered in more than 50% of space crew members. There is strong evidence that such effect is due to stress rather than to weightlessness per se. However the health of astronauts was never threatened so far. Experiments in-vitro with cultures of human peripheral blood lymphocytes (not from astronauts) have shown that T cell function is dramatically reduced. Recent work with the random positioning machine, a new instrument to simulate conditions similar to microgravity, indicate that there are direct gravitational effects on the genetic expression of interleukin-2 and of its receptor in T lymphocytes.

Prevention of a first episode of variceal bleeding: role of duplex Doppler sonographic measurement of the acute response to beta-blockers

The aim of our study was to assess whether acute variations in portal vein Doppler sonographic parameters induced by administration of a single beta-blocker agent are predictive of the long-term effects of these drugs in the prevention of a first episode of variceal bleeding. In 30 patients with liver cirrhosis at high risk for variceal bleeding, duplex Doppler sonographic parameters (maximal portal flow velocity, portal blood flow, and congestion index) were measured before and 4 h after the administration of 40 mg of propranolol. Twenty-three of these patients started chronic therapy with propanolol and were evaluated periodically (seven patients were excluded because they did not continue the therapy). The percentage of patients free from bleeding was 86.9% at the first year and 77.8% at the second year. Among a series of clinical, laboratory, and instrument-based parameters, the only one related to first bleeding, selected by the Cox regression model, was the percentage decrease in maximal portal flow velocity observed after initial administration of propranolol (P < 0.01). The best cutoff value for the percentage decrease in portal flow velocity (portal flow velocity test) was 12%. The prevalence of bleeding had been 25% (3 of 12) in patients with positive portal flow velocity test results (12% decrease or more), versus 64% (7 of 11) in patients with negative portal flow velocity test results. The actuarial probability of remaining free from bleeding (Kaplan-Meier analysis) was different in these two groups (log rank P < 0.01). The portal flow velocity test represents a safe and feasible method to predict the efficacy of beta-blockers in the prevention of a first bleeding episode in patients with cirrhosis. In patients with negative results on the portal flow velocity test, an alternative therapeutic approach should be considered.

Metabolic indicators of oxidative stress correlate with haemichrome attachment to membrane, band 3 aggregation and erythrophagocytosis in beta-thalassaemia intermedia

Haematological data, genotype, transfusion requirements, metabolic indicators of oxidative stress (flux via hexose-monophosphate shunt (HMPS); steady state level of GSH and GSSG, NADPH and NADP; activity of anti-oxidant enzymes), parameters of membrane damage (aggregated band 3; membrane-bound haemichromes, autologous immunoglobulins (Igs) and C3 complement fragments) and erythrophagocytosis were measured in erythrocytes (RBC) of 15 beta-thalassaemia intermedia patients (nine splenectomized) with low, if any, transfusion requirements. Patients presented increased aggregated band 3, bound haemichromes, Igs and C3 complement fragments, and increased erythrophagocytosis. Bound haemichromes strongly correlated with aggregated band 3. Anti-band 3 Igs were predominantly associated with aggregated band 3. Erythrophagocytosis positively correlated with aggregated band 3, haemichromes and Igs, suggesting the involvement of haemichrome-induced band 3 aggregation in phagocytic removal of beta-thalassaemic RBC. Splenectomized patients showed higher degrees of membrane damage and phagocytosis, significantly higher numbers of circulating RBC precursors, and tendentially higher numbers of reticulocytes. Basal flux via HMPS was increased twofold, but HMPS stimulation by methylene blue was decreased, as was the glucose flux via HMPS. GSH was remarkably decreased, whereas NADPH was increased. Except for unchanged catalase and glutathione reductase, anti-oxidant enzymes had increased activity. Negative correlation between HMPS stimulation by methylene blue and bound haemichromes indicated that the ability to enhance HMPS may counteract haemichrome precipitation and limit consequent membrane damage leading to erythrophagocytosis.

Identification of HIV patients with active pulmonary tuberculosis using urine based polymerase chain reaction assay

BACKGROUND

Despite the increased dissemination of tuberculosis among HIV infected patients, the diagnosis is difficult to establish. Traditional microbiological methods lack satisfactory sensitivity. We have developed a highly sensitive and specific nested polymerase chain reaction (PCR) capable of detecting Mycobacterium tuberculosis DNA in urine specimens and have used this test to examine urine specimens from HIV patients with active pulmonary tuberculosis.

METHODS

Urine specimens from 13 HIV infected patients with microbiologically proven active pulmonary tuberculosis, 10 AIDS patients with non-tuberculous mycobacterial infection (documented by blood culture), 53 AIDS patients with no evidence of mycobacterial disease, and 80 healthy subjects (25 with positive skin test to purified protein derivative) were tested for M tuberculosis using PCR, acid fast staining (AFS), and culture.

RESULTS

Of the urine specimens from patients with active tuberculosis, all tested positive by PCR, two by culture, and none by AFS. No reactivity was observed in urine specimens from patients with non-tuberculous mycobacterial infection. Of the 53 AIDS patients without mycobacterial infection, one had a positive urine PCR. Normal subjects were all negative.

CONCLUSIONS

Urine based nested PCR for M tuberculosis may be a useful test for identifying HIV patients with pulmonary tuberculosis.

Castleman's disease

Castleman's disease (CD) is a rare atypical lymphoproliferative disorder whose morphology, soon after the original presentation of Castleman et al., has been definitely subdivided in a hyaline vascular (HV) and plasma cell (PC) histopathological pattern, with intermediate variants. The former occurs much more frequently than the latter and is usually localized to the mediastinum or pulmonary hilum. The latter involves lymph nodes separately or in aggregations and often displays multicentricity with systemic symptoms including autoimmune phenomena and aggressive course. Infections are the most frequent causes of patient demise in these cases, followed by malignancies such as Kaposi's sarcoma, malignant lymphoma or epithelial neoplasia. Increase of follicular dendritic reticulum cells (FDRC), often dysplastic, in the germinal center (GC) and marginal zone (MZ), broad MZ expansion with prominence of immunophenotypically aberrant B cells (Ki B3-negative, CD5-positive), possible predominance of paracortical plasma cells often with clusters of clonal l-light chain restricted plasma cells, increase of paracortical plasmacytoid monocytes, represent common hallmarks of CD. However, small hyalinized and hypervascular GCs with hypervascular interfollicular stroma and sinus effacement are common features of the HV variant, whereas hyperplastic GCs with plasma cell aggregates in lymph node paracortex and partially spared sinuses are characteristic features of the PC variant. The frequent concomitance of the HV and PC types at separate sites, together with transient morphological patterns from one type to the other and from the localized to multicentric form during the course of the disease, along with B and T cell impaired functions, with frequent development of autoantibodies, have suggested that CD is a single disorder related to immune dysregulation. A key event in the pathogenesis of CD has been recently suggested to be an abnormal production of a B cell growth factor, such as IL-6, leading to lymphoproliferation and plasma cell differentiation and being involved in the oncogenesis of plasmacytoma. In this event, Kaposi's sarcoma associated virus (HHV-8), which has been found in many cases of CD, especially in the multicentric form, could play a crucial role both in producing IL-6 and releasing angiogenic factors. A possible differentiation block may lead to the development of a malignant lymphoma. Kaposi's sarcoma or other malignant neoplasias can be supposed to be consequences of the immunodeficiency typical of CD.

Early phagocytosis of glucose-6-phosphate dehydrogenase (G6PD)-deficient erythrocytes parasitized by Plasmodium falciparum may explain malaria protection in G6PD deficiency

In population-based studies it has been established that inherited deficiency of erythrocyte (E) glucose-6-phosphate dehydrogenase (G6PD) confers protection against severe Plasmodium falciparum (P falciparum) malaria. Impaired growth of parasites in G6PD-deficient E in vitro has been reported in some studies, but not in others. In a systematic analysis, we have found that with five different strains of P falciparum (FCR-3, KI, C10, HB3B, and T9/96), there was no significant difference in either invasion or maturation when the parasites were grown in either normal or G6PD-deficient (Mediterranean variant) E. With all of these strains and at different maturation stages, we were unable to detect any difference in the amount of P falciparum-specific G6PD mRNA in normal versus deficient parasitized E. The rate of 14C-CO2 production from D-[1-14C] glucose (which closely reflects intracellular activity of G6PD) contributed by the parasite was very similar in intact normal and deficient E. By contrast, in studies of phagocytosis of parasitized E by human adherent monocytes, we found that when the parasites were at the ring stage (ring-stage parasitized E [RPE]), deficient RPE were phagocytosed 2.3 times more intensely than normal RPE (P = .001), whereas there was no difference when the parasites were at the more mature trophozoite stage (trophozoite-stage parasitized E [TPE]). Phagocytic removal markers (autologous IgG and complement C3 fragments) were significantly higher in deficient RPE than in normal RPE, while they were very similar in normal and deficient TPE. The level of reduced glutathione was remarkably lower in deficient RPE compared with normal RPE. We conclude that impaired antioxidant defense in deficient RPE may be responsible for membrane damage followed by phagocytosis. Because RPE, unlike TPE, are nontoxic to phagocytes, the increased removal by phagocytosis of RPE would reduce maturation to TPE and to schizonts and may be a highly efficient mechanism of malaria resistance in deficient subjects.

Simulated microgravity inhibits the genetic expression of interleukin-2 and its receptor in mitogen-activated T lymphocytes

Experiments conducted in space in the last two decades have shown that T lymphocyte activation in vitro is remarkably reduced in microgravity. The data indicate that a failure of the expression of the interleukin-2 receptor (measured as protein secreted in the supernatant) is responsible of the loss of activity. To test such hypothesis we have studied the genetic expression of interleukin-2 and of its receptor in concanavalin A-activated lymphocytes with the RT-PCR technology. Microgravity conditions were simulated in the fast rotating clinostat and in the random positioning machine. The latter is an instrument introduced recently to study gravitational effects on single cells. Our data clearly show that the expression of both IL-2 and IL-2Ralpha genes is significantly inhibited in simulated O X g. Thus full activation is prevented.

Neutrophils and monocytes from subjects with the Mediterranean G6PD variant: effect of Plasmodium falciparum hemozoin on G6PD activity, oxidative burst and cytokine production

Glucose 6-phosphate dehydrogenase (G6PD) activity and oxidative burst were measured in neutrophils and monocytes from five, hemizygous, G6PD-deficient (Mediterranean variant) individuals and five normal controls. Additionally, tumor necrosis factor (TNF), interleukin-10 (IL-10), interleukin-12 (IL-12) release and phagocytosis of the malarial pigment hemozoin or opsonized erythrocytes (RBC) were measured in monocytes recovered from G6PD-deficient and normal individuals. G6PD activity was significantly lower in "deficient monocytes" (38% residual activity, p = 0.01) and not significantly different in "deficient neutrophils" (79% residual activity, p = 0.83) compared to homologous leukocytes recovered from normal controls. Oxidative burst was not significantly different in "deficient" versus "normal" neutrophils and monocytes. Previous phagocytosis of hemozoin decreased the phorbol ester induced oxidative burst in "deficient" and "normal" monocytes but not in neutrophils. Phagocytosis of hemozoin and RBC strongly stimulated cytokine production. With the exception of IL-10, the cytokine production pattern was comparable in "deficient" versus "normal" cells. Incubation with high concentrations of hemozoin (equivalent to 300 RBC per monocyte) strongly stimulated TNF production. Lipopolysaccharide (LPS) had an additive effect on TNF production induced by hemozoin or opsonized RBC. IL-12 production was induced only by the presence of large amounts of hemozoin. IL-10 production was increased in normal monocytes incubated with RBC or hemozoin. LPS increased IL-10 production significantly in monocytes incubated with RBC or low amounts of hemozoin (equivalent to 30 RBC per monocyte), but had no effect when given alone or in conjunction with high concentrations of hemozoin. Interestingly, deficient monocytes produced less IL-10 than normal cells under these conditions. In conclusion, except for IL-10 production, we did not find major functional differences between neutrophils and monocytes from individuals with or without the Mediterranean G6PD mutation.

Indices of membrane alterations in beta-thalassemic erythrocytes

Analytical protocols for the study of thalassemic erythrocyte membrane alterations are described. Denatured hemoglobin derivatives and aggregated band 3 are separated from detergent membrane extracts by gel-filtration as high-molecular-weight aggregates and quantitated spectrophotometrically. Membrane-bound, low-molecular-weight iron is measured on SDS-solubilized ghosts by a ferrozine-based colorimetric test. We adapted these methods for microscale preparation and analysis of erythrocyte ghosts in order to have suitable tools to estimate oxidative membrane damage in human samples. Data from 11 beta-thalassemia intermedia patients and from 10 normal controls are reported as an example of the application of these methods.

Decreased band 3 anion transport activity and band 3 clusterization in congenital dyserythropoietic anemia type II

Congenital dyserythropoietic anemia type II (CDA-II) is the most common form of inherited dyserythropoiesis. Erythroid precursor and red blood cells (RBCs) show characteristic morphological abnormalities. Biochemical studies have shown that this disease is associated with reduced glycosylation activity, which endows band 3 (anion transporter) with peculiar characteristics. The life span of RBCs may be shortened in patients with CDA-II, a phenomenon that has been ascribed to this membrane defect. We analyzed seven unrelated patients with CDA-II and five control subjects. In all of the CDA-II patients, erythrocytes presented a band 3 that was thinner than usual and also migrated slightly faster on SDS-PAGE. Analysis of anion transport function in CDA-II RBC samples demonstrated decreased anion exchange activity per band 3 molecule. Furthermore, we observed that the CDA-II RBCs contained larger amounts of aggregate band 3 than control erythrocytes. Aggregate band 3 has been reported to bind naturally occurring antibodies that mediate the phagocytic removal of RBCs. We provide evidence that both the phagocytic index (RBCs/macrophage) and the amount of membrane-bound immunoglobulin (IgG) are elevated in CDA-II erythrocytes. Our results suggest that the mild hemolysis observed in patients with CDA-II may be ascribed to clusterization of band 3, which leads to IgG binding and phagocytosis, and not to a secondary modification of the cytoskeletal structure of RBCs.

Plasmodium falciparum glutathione metabolism and growth are independent of glutathione system of host erythrocyte

Plasmodium falciparum parasites grew normally in glutathione (GSH)-depleted normal and G6PD-deficient (Mediterranean variant) erythrocytes (RBC). Growth inhibition was observed only at less than approximately 6-12% residual GSH. Parasites studied separately with the Sendai virus technique synthesized GSH de novo and regenerated reduced GSH 10-20 times faster than non-parasitized RBC. Electron spin resonance measurement of Tempol reduction indicated that the ability to reduce free radicals was restricted to the parasite. The marked efflux of oxidized GSH was mainly derived from the parasite. In conclusion, parasites are endowed with powerful and host-independent mechanisms which de novo synthesize or regenerate GSH and allow undisturbed parasite development in GSH-depleted RBC.

Mesenteric vein thrombosis: a rare cause of abdominal pain in cirrhotic patients--two case reports

Mesenteric vein thrombosis is a rare disorder which can develop rapidly with intestinal infarction or subacutely with abdominal pain due to intestinal ischemia. Despite the availability of modern diagnostic tools, which allow an early diagnosis in most cases, the mortality from this disease has not significantly diminished over the years. The problem is that the syndrome is rare and unusual and the clinical presentation is usually vague or confusing. Particularly in cirrhotic patients, this diagnosis requires the exclusion of several other complications of liver disease, like spontaneous bacterial peritonitis, tense ascites or portal thrombosis. Here, we report the occurrence of acute mesenteric vein thrombosis in two patients with liver cirrhosis. Severe subcontinuous abdominal pain out of proportion to the physical findings and abdominal distension were the major symptoms in both patients. Magnetic resonance imaging in one case and ultrasound scan with color Doppler followed by computed tomography in the other patient confirmed the diagnosis and enabled an appropriate early therapy to be undertaken.

Characterization of membrane surface proteins of Mycoplasma agalactiae during natural infection

We have analyzed antigenic variation of seven M. agalactiae wild strains using different sera from naturally infected sheep. Only 30 day sera recognized all surface proteins and inhibited the growth of mycoplasmas. Furthermore, we have observed that two strongly immunogenic proteins: 55 and 35 kDa were digested using 500 micrograms/ml of trypsin. These two bands are immunoprecipitated together with four other proteins but only the 35 kDa protein is recognized by eluted antibodies.

Detection of Mycobacterium tuberculosis by PCR analysis of urine and other clinical samples from AIDS and non-HIV-infected patients

A number of different clinical specimens, such as sputum, cerebrospinal fluid and blood, have been reported to be good substrates for the detection of Mycobacterium tuberculosis by PCR assay. We wanted to search for the presence of mycobacteria in other body fluids, such as urine. Urine samples and other samples obtained from AIDS patients and non HIV-infected patients were analysed by PCR. The results were compared with those obtained using conventional methods (Bactec 460 TB and AFB (acid fast bacilli strain)). We analysed 412 urine samples and 210 different other samples (sputum and cerebrospinal fluid) obtained from AIDS patients by PCR; almost identical levels of PCR-positive (14-17%) results were observed in all samples analysed. The results were then compared with those obtained with the Bactec 460 TB and AFB. PCR, Bactec 460 TB and acid fast stain were also used to analyse 190 urine samples and 230 other samples from non-HIV infected patients in the consumption ward of Sassari Hospital. The number of urine samples positive by PCR (6.3%) and Bactec 460 TB (2.1%) was half that obtained from samples taken from the AIDS patients. As expected, an increase in the number of positive sputum samples was observed with all methods. The results indicate that PCR analysis of urine samples represents a valid alternative for fast and sensitive detection of M. tuberculosis. This method can be routinely used in the clinical laboratory, especially in HIV-infected patients.

Value of the measurement of portal flow velocity in the differential diagnosis of asymptomatic splenomegaly

AIM AND METHODS

This prospective study was carried on 20 patients (10 with liver cirrhosis and 10 with myelo-lymphoproliferative disorders), consecutively admitted to our ward for splenomegaly and thrombocytopenia, with the aim of evaluating the ability of Duplex-Doppler ultrasonography (DDUS) to discriminate between congestive splenomegaly and enlarged spleen caused by haematological disorders.

RESULTS

Comparing the clinical/laboratory and DDUS findings for the two groups, it emerged that maximum-portal flow velocity (PFV) values revealed the most statistically significant differences: 17.31 SD 2.48 vs. 28.27 SD 3.53 (cm/s, P < 0.001). Discriminant analysis showed that max-PFV is the variable which by itself maximizes the separation between the two groups (F = 71.56; P < 0.0001). The patients with congestive splenomegaly exhibited lower max-PFV than the controls (17.31 SD 2.48 vs. 26.29 SD 2.38 cm/s, P < 0.001), unlike those with haematological diseases, whose max-PFV values were greater, albeit not significantly so (28.27 SD 3.53 vs. 26.29 SD 2.38 cm/s, P = 0.161).

CONCLUSIONS

DDUS assessment of portal haemodynamics thus proved useful in the differential diagnosis of splenomegaly in asymptomatic patients since it distinguishes rapidly and non-invasively between congestive and haemotological splenomegaly. A lower-than-normal max-PFV value indicates congestive splenomegaly; a highish value, on the other hand, suggests a splenomegaly of haematological origin.

[The use of echo-guided fine-needle biopsy in the diagnosis of nodular hepatic lesions]

211 patients were submitted to percutaneous ultrasound-guided liver biopsy: 184 patients (87.2%) had only one focal lesion, the other 27 had two or more lesions. In 9 patients (4.27%) the material drawn out from the liver was not adequate for microscopic examination (Retrieval Rate 95.7%). Histological evaluation revealed: absence of neoplasm in 67 patients (31.75%), benign lesion in 29 patients (13.74%), primitive malignant lesion in 70 patients (33.18%) and metastatic malignant lesion in 36 patients (17.06%). Combining the histological data with disease manifestation, biopsy showed a sensitivity of 95.1%, specificity of 100%, positive predictive value of 100%, negative predictive value of 89.4% and a diagnostic accuracy of 92.4%. None of the most important complications described in literature was observed. Our study confirms that ultrasound guided biopsy is a procedure of high diagnostic value in patients with nodular liver lesions, advantageous for its simplicity, low cost and safety.

Antimalarial drugs inhibit the phagocytosis of erythrocytes infected with Plasmodium falciparum

Phagocytic cells constitute the first line of defence against malarial parasites. They perform their role by delivering oxidative radicals and by phagocytosing infected red blood cells (IRBC). Phagocytosis is mediated by antibody binding to clustered band 3 antigen in the IRBC membrane and activation of the alternative complement pathway. In this study we showed that treatment of IRBC containing Plasmodium falciparum with therapeutically-relevant concentrations of antimalarial drugs considerably reduced the binding of immunoglobulin G (IgG) to, and the phagocytosis of, IRBC. Opsonization of IRBC by fresh serum before drug treatment prevented this inhibitory action of drugs. Removal of the drug restored IgG binding and the phagocytic susceptibility of IRBC in a time-dependent fashion. Direct measurement of the effect of chloroquine on the clustering of band 3 in IRBC, however, failed to reveal any disruption of the aggregation. We conclude that antimalarial drugs are able to alter, by an as yet unresolved mechanism, the affinity of IgG to clustered band 3. This affinity of IRBC seems to be determined by a dynamic process that depends on the metabolic activity of the parasite.

Does the measurement of portal flow velocity have any value in the identification of patients with cirrhosis at risk of digestive bleeding?

Upper gastrointestinal bleeding is a leading cause of death in patients with liver cirrhosis. In most cases haemorrhage originates from oesophageal varices or from congestive gastropathy, and the evaluation of the bleeding risk is based on oesophagogastroduodenoscopic data. The aim of this prospective study was to determine whether the measurement of portal flow velocity by Duplex-Doppler, compared with endoscopic data, can help in detecting patients with cirrhosis at risk of bleeding. One hundred and seventy-three patients underwent endoscopy to ascertain the size of the varices and the severity of congestive gastropathy. For each patient maximal portal flow velocity measurements were obtained. No difference in portal flow velocity was observed between patients with or without oesophageal varices or congestive gastropathy. During a 2-year observation period, 27 patients (15.6%) had at least one episode of acute digestive bleeding. Stepwise multiple logistic regression analysis demonstrated a correlation between oesophageal varices and congestive gastropathy endoscopic grading and the incidence of bleeding; only the former was entered into the final regression equation (p < 0.001). No relationship between the max portal flow velocity value and incidence of bleeding was found. This study shows that portal flow velocity is unrelated to the degree of the endoscopic abnormalities in patients with liver cirrhosis and that it has no value in the identification of patients with cirrhosis at risk of upper gastrointestinal bleeding.

Role of hemichrome binding to erythrocyte membrane in the generation of band-3 alterations in beta-thalassemia intermedia erythrocytes

Nine splenectomized, hematologically well-compensated beta-thalassemia intermedia patients randomly chosen from a pool of 60 similar patients were studied. Membrane proteins solubilized with nondenaturing detergent C12E8 were gel filtered on Sepharose CL-6B (Pharmacia Fine Chemicals, Uppsala, Sweden). Fractions containing higher than 4,000-kD molecular-weight aggregates were isolated and analyzed. Four patients had remarkably increased amounts of membrane-bound hemichromes and Igs. In those patients, band 3 underwent oxidative modifications such as aggregation and a decrease in sulfhydryl groups. The other five patients had low amounts of membrane-bound hemichromes and less modifications of band 3. The same band-3 modifications could be reproduced by challenging normal membranes with artificially generated hemichromes or with hemolysates prepared from thalassemic erythrocytes of the high-hemichrome group. Addition of reduced glutathione to the challenged membranes did not hinder hemichrome binding, but prevented oxidative modifications of band 3 and Ig binding to high-molecular-weight band-3 aggregates. Hemichrome binding to band 3, hemichrome-mediated oxidation of band-3 cytoplasmic domains, generation of high-molecular-weight band-3 aggregates, and enhanced opsonization by anti-band-3 antibodies is a possible sequence of events leading to phagocytic removal of erythrocytes in thalassemia.

Effects of propranolol compared with clonidine on portal haemodynamics: a double-blind cross-over study using duplex-Doppler ultrasonography

BACKGROUND

Patients with liver cirrhosis and large oesophageal varices run a high risk of digestive haemorrhage due to the rupture of oesophageal varices, an event associated with a high mortality. At present, the only treatment for the prevention of first bleeding from oesophageal varices on which there is general agreement is drug-based. In order to tailor drug treatment to the requirements of individual patients more precisely, an ever-increasing number of drugs is being investigated.

DESIGN

Double-blind cross-over study.

METHODS

Sixteen cirrhotic patients with large oesophageal varices were studied by means of duplex-Doppler ultrasonography to determine variations in portal haemodynamics after oral administration of 0.150 mg clonidine and to compare these with the variations observed after oral administration of 40 mg propranolol.

RESULTS

Propranolol caused a significant reduction in maximum portal flow velocity (P < 0.001), whereas clonidine failed to cause any such variation (P = 0.194). Considering as responders those patients who exhibited at least a 10% decrease in maximum portal flow velocity, 11 patients responded to propranolol; of these, three also responded to clonidine. No patient responded only to clonidine.

CONCLUSION

The absence of any effects on the parameters of portal haemodynamics would appear to deny clonidine any significant role in preventing first bleeding resulting from the rupture of oesophageal varices.

A luminescence method for the quantitative determination of phagocytosis of erythrocytes, of malaria-parasitized erythrocytes and of malarial pigment

A method is described for the quantitative measurement of phagocytosis of human erythrocytes, malaria-parasitized erythrocytes and isolated malarial pigment by adherent human monocytes. The method utilizes measurement of haem-elicited luminescence both for the assay of ingested haemoglobin or malarial pigment haem and for the quantification of adherent monocytes. The latter is based on assay of luminescence elicited by cytochrome haem. The method utilizes the same low-cost reagents and equipment for assay of ingested haem and for quantification of adherent monocytes. The method is fast and extremely sensitive. The lower sensitivity limit is 500 monocytes and 10 RBC, or RBC equivalents in the case of malarial pigment, per assay. A detailed protocol with full calculations of a typical phagocytosis experiment of oxidatively damaged RBC, malarial pigment and control RBS is presented.

Binding of naturally occurring antibodies to oxidatively and nonoxidatively modified erythrocyte band 3

Both oxidative clustering (elicited by diamide treatment) and nonoxidative clustering (elicited by zinc/BS3 (bis[sulfosuccinimidyl]suberate) treatment) of erythrocyte integral membrane proteins induce binding of autologous antibodies with anti-band 3 specificity, followed by complement deposition and phagocytosis. Autologous antibodies eluted from nonoxidatively clustered erythrocytes bind to and stimulate phagocytosis of oxidatively damaged erythrocytes. Those eluted antibodies bind specifically to disulfide-crosslinked band 3 dimers generated by diamide treatment. Band 3 dimerization and antibody binding are abrogated by cleavage of band 3 cytoplasmic domain. Thus, disulfide-crosslinked band 3 dimers are the minimal band 3 aggregate with enhanced affinity for anti-band 3 antibodies. The eluted antibodies do not bind to band 3 dimers generated nonoxidatively by BS3 treatment but bind avidly to larger band 3 clusters generated nonoxidatively by zinc/BS3 treatment. Possibly, disulfide crosslinking of cytoplasmic domain cysteines induces reorientation of intramembrane domains as to expose putative anti-band 3 epitopes and allow bivalent binding of anti-band 3 antibodies. Extensive nonoxidative band 3 clustering appears to disrupt the native band 3 conformation and generate reoriented dimers which expose putative anti-band 3 epitopes in the proper distance and orientation as to allow bivalent antibody binding.