SF3B1 mutations provide genetic vulnerability to copper ionophores in human acute myeloid leukemia

In a phenotypical screen of 56 acute myeloid leukemia (AML) patient samples and using a library of 10,000 compounds, we identified a hit with increased sensitivity toward SF3B1-mutated and adverse risk AMLs. Through structure-activity relationship studies, this hit was optimized into a potent, specific, and nongenotoxic molecule called UM4118. We demonstrated that UM4118 acts as a copper ionophore that initiates a mitochondrial-based noncanonical form of cell death known as cuproptosis. CRISPR-Cas9 loss-of-function screen further revealed that iron-sulfur cluster (ISC) deficiency enhances copper-mediated cell death. Specifically, we found that loss of the mitochondrial ISC transporter ABCB7 is synthetic lethal to UM4118. ABCB7 is misspliced and down-regulated in SF3B1-mutated leukemia, creating a vulnerability to copper ionophores. Accordingly, ABCB7 overexpression partially rescued SF3B1-mutated cells to copper overload. Together, our work provides mechanistic insights that link ISC deficiency to cuproptosis, as exemplified by the high sensitivity of SF3B1-mutated AMLs. We thus propose SF3B1 mutations as a biomarker for future copper ionophore-based therapies.

Bicc1 ribonucleoprotein complexes specifying organ laterality are licensed by ANKS6-induced structural remodeling of associated ANKS3

Organ laterality of vertebrates is specified by accelerated asymmetric decay of Dand5 mRNA mediated by Bicaudal-C1 (Bicc1) on the left side, but whether binding of this or any other mRNA to Bicc1 can be regulated is unknown. Here, we found that a CRISPR-engineered truncation in ankyrin and sterile alpha motif (SAM)-containing 3 (ANKS3) leads to symmetric mRNA decay mediated by the Bicc1-interacting Dand5 3' UTR. AlphaFold structure predictions of protein complexes and their biochemical validation by in vitro reconstitution reveal a novel interaction of the C-terminal coiled coil domain of ANKS3 with Bicc1 that inhibits binding of target mRNAs, depending on the conformation of ANKS3 and its regulation by ANKS6. The dual regulation of RNA binding by mutually opposing structured protein domains in this multivalent protein network emerges as a novel mechanism linking associated laterality defects and possibly other ciliopathies to perturbed dynamics in Bicc1 ribonucleoparticle (RNP) formation.

Antagonistic interactions among structured domains in the multivalent Bicc1-ANKS3-ANKS6 protein network govern phase transitioning of target mRNAs

The growing number of diseases linked to aberrant phase transitioning of ribonucleoproteins highlights the need to uncover how the interplay between multivalent protein and RNA interactions is regulated. Cytoplasmic granules of the RNA binding protein Bicaudal-C (Bicc1) are regulated by the ciliopathy proteins ankyrin (ANK) and sterile alpha motif (SAM) domain-containing ANKS3 and ANKS6, but whether and how target mRNAs are affected is unknown. Here, we show that head-to-tail polymers of Bicc1 nucleated by its SAM domain are interconnected by K homology (KH) domains in a protein meshwork that mediates liquid-to-gel transitioning of client transcripts. Moreover, while the dispersion of these granules by ANKS3 concomitantly released bound mRNAs, co-recruitment of ANKS6 by ANKS3 reinstated Bicc1 condensation and ribonucleoparticle assembly. RNA-independent Bicc1 polymerization and its dual regulation by ANKS3 and ANKS6 represent a new mechanism to couple the reversible immobilization of client mRNAs to controlled protein phase transitioning between distinct metastable states.

Role of Bicaudal C1 in renal gluconeogenesis and its novel interaction with the CTLH complex

Altered glucose and lipid metabolism fuel cystic growth in polycystic kidneys, but the cause of these perturbations is unclear. Renal cysts also associate with mutations in Bicaudal C1 (Bicc1) or in its self-polymerizing sterile alpha motif (SAM). Here, we found that Bicc1 maintains normoglycemia and the expression of the gluconeogenic enzymes FBP1 and PEPCK in kidneys. A proteomic screen revealed that Bicc1 interacts with the C-Terminal to Lis-Homology domain (CTLH) complex. Since the orthologous Gid complex in S. cerevisae targets FBP1 and PEPCK for degradation, we mapped the topology among CTLH subunits and found that SAM-mediated binding controls Bicc1 protein levels, whereas Bicc1 inhibited the accumulation of several CTLH subunits. Under the conditions analyzed, Bicc1 increased FBP1 protein levels independently of the CTLH complex. Besides linking Bicc1 to cell metabolism, our findings reveal new layers of complexity in the regulation of renal gluconeogenesis compared to lower eukaryotes.

Polycystic kidney diseases (PKD) are incurable inherited chronic disorders marked by fluid-filled cysts that frequently cause renal failure. A glycolytic metabolism reminiscent of cancerous cells accelerates cystic growth, but the mechanism underlying such metabolic re-wiring is poorly understood. PKD-like cystic kidneys also develop in mice that lack the RNA-binding protein Bicaudal-C (Bicc1), and mutations in a single copy of human BICC1 associate with renal cystic dysplasia. Here, we report that Bicc1 regulates renal gluconeogenesis. A screen for interacting factors revealed that Bicc1 binds the C-Terminal to Lis-Homology domain (CTLH) complex, which in lower eukaryotes mediates degradation of gluconeogenic enzymes. By contrast, Bicc1 and the mammalian CTLH complex regulated each other, and Bicc1 stimulated the accumulation of the rate-limiting gluconeogenic enzyme even in cells depleted of CTLH subunits. Our finding that Bicc1 is required for normoglycemia implies that renal gluconeogenesis may be important to inhibit cyst formation.

Crystal Structure of Bicc1 SAM Polymer and Mapping of Interactions between the Ciliopathy-Associated Proteins Bicc1, ANKS3, and ANKS6

Head-to-tail polymers of sterile alpha motifs (SAM) can scaffold large macromolecular complexes. Several SAM-domain proteins that bind each other are mutated in patients with cystic kidneys or laterality defects, including the Ankyrin (ANK) and SAM domain-containing proteins ANKS6 and ANKS3, and the RNA-binding protein Bicc1. To address how their interactions are regulated, we first determined a high-resolution crystal structure of a Bicc1-SAM polymer, revealing a canonical SAM polymer with a high degree of flexibility in the subunit interface orientations. We further mapped interactions between full-length and distinct domains of Bicc1, ANKS3, and ANKS6. Neither ANKS3 nor ANKS6 alone formed macroscopic homopolymers in vivo. However, ANKS3 recruited ANKS6 to Bicc1, and the three proteins together cooperatively generated giant macromolecular complexes. Thus, the giant assemblies are shaped by SAM domains, their flanking sequences, and SAM-independent protein-protein and protein-mRNA interactions.

Decay pattern of pygmy states observed in neutron-rich 26Ne

Coulomb excitation of the exotic neutron-rich nucleus (26)Ne on a (208)Pb target was measured at 58 MeV/u in order to search for low-lying E1 strength above the neutron emission threshold. This radioactive beam experiment was carried out at the RIKEN Accelerator Research Facility. Using the invariant mass method in the 25Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV excitation energy. By performing a multipole decomposition of the differential cross section, a reduced dipole transition probability of B(E1)=0.49+/-0.16e(2) fm(2) is deduced, corresponding to 4.9+/-1.6% of the Thomas-Reiche-Kuhn sum rule. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is measured. The extracted decay pattern is not consistent with several mean-field theory descriptions of the pygmy states.

Silencing of the MT1-MMP/ G6PT axis suppresses calcium mobilization by sphingosine-1-phosphate in glioblastoma cells

The contributions of membrane type-1 matrix metalloproteinase (MT1-MMP) and of the glucose-6-phosphate transporter (G6PT) in sphingosine-1-phosphate (S1P)-mediated Ca(2+) mobilization were assessed in glioblastoma cells. We show that gene silencing of MT1-MMP or G6PT decreased the extent of S1P-induced Ca(2+) mobilization, chemotaxis, and extracellular signal-related kinase phosphorylation. Chlorogenic acid and (-)-epigallocatechin-3-gallate, two diet-derived inhibitors of G6PT and of MT1-MMP, respectively, reduced S1P-mediated Ca(2+) mobilization. An intact MT1-MMP/G6PT signaling axis is thus required for efficient Ca(2+) mobilization in response to bioactive lipids such as S1P. Targeted inhibition of either MT1-MMP or G6PT may lead to reduced infiltrative and invasive properties of brain tumor cells.

Tetra- and hexavalent mannosides inhibit the pro-apoptotic, antiproliferative and cell surface clustering effects of concanavalin-A: impact on MT1-MMP functions in marrow-derived mesenchymal stromal cells

Mesenchymal stromal cells (MSC) mobilization and recruitment by experimental vascularizing tumors involves membrane type 1-matrix metalloproteinase (MT1-MMP) functions. Given that the mannose-specific lectin Concanavalin-A (ConA) induces MT1-MMP expression and mimics biological lectins/carbohydrate interactions, we synthesized and tested the potential of 11 mannoside clusters to block ConA activities on MSC. We found that tetra- and hexavalent mannosides reversed ConA-mediated changes in MSC morphology and antagonized ConA-induced caspase-3 activity and proMMP-2 activation. Tetra- and hexavalent mannosides also inhibited ConA- but not the cytoskeleton disrupting agent Cytochalasin-d-induced MT1-MMP cell surface proteolytic processing mechanisms, and effects on cell cycle phase progression. The antiproliferative and pro-apoptotic impact of ConA on the MT1-MMP/glucose-6-phosphate transporter signaling axis was also reversed by these mannosides. In conclusion, we designed and identified glycocluster constructions that efficiently interfered with carbohydrate-binding proteins (lectins) interaction with oligosaccharide moieties of glycoproteins at the cell surface of MSC. These glycoclusters may serve in carbohydrate-based anticancer strategies through their ability to specifically target MT1-MMP pleiotropic functions in cell survival, proliferation, and extracellular matrix degradation.

Short-term benefits and risks of intravenous iron: a systematic review and meta-analysis

BACKGROUND

Intravenous (IV) iron may correct anemia more efficiently than oral iron, but it has been associated with allergic and hemodynamic reactions, and it may increase the risks of infectious complications. The objective of this systematic review and meta-analysis was to clarify these controversial issues.

STUDY DESIGN AND METHODS

Studies evaluating the use of IV iron compared to enteral or no iron with outcomes within 2 months of treatment initiation were identified. Only randomized controlled trials were included. When a meta-analysis was possible, studies were combined with the Review Manager of the Cochrane Collaboration Group 2003. Statistics were calculated as standardized mean differences (SMDs), with a random-effect model.

RESULTS

Thirteen studies met inclusion criteria. Meta-analysis revealed a significant increase in the reticulocyte count (SMD, 0.70; 95% confidence interval [CI], 0.10-1.29; p = 0.02) and in ferritin levels (SMD, 1.18; 95% CI, 0.69-1.68; p = 0.00001), but it also showed that in such a short period of time, IV iron does not correct hemoglobin (Hb)-hematocrit (Hct) better than enteral or no iron. In a sensitivity analysis, however, the increase in Hb-Hct became significant in the nondextran group (SMD, 0.27; 95% CI, 0.04-0.51; p = 0.02). No increase in transferrin saturation was observed. Meta-analysis of the allergic and hemodynamic reactions was not possible as most studies did not clearly describe these outcomes.

CONCLUSION

Our results suggest that treatment with nondextran IV iron may benefit a wide variety of patients. Randomized controlled studies are definitively needed to further evaluate the usefulness and safety of IV iron.

Necrosis induction in glioblastoma cells reveals a new "bioswitch" function for the MT1-MMP/G6PT signaling axis in proMMP-2 activation versus cell death decision

Cytoskeleton disorganization is an early step in the activation process of matrix metalloproteinase 2 (MMP-2) by membrane type 1 MMP (MT1-MMP) but is also associated with endoplasmic reticulum (ER) dysfunction and subsequent cell death. Given evidence that the ER-embedded glucose-6-phosphate transporter (G6PT) regulates glioblastoma cell survival and that MT1-MMP is a key enzyme in the cancer cell invasive phenotype, we explored the molecular link between G6PT and MT1-MMP. Cytoskeleton-disrupting agents such as concanavalin A (ConA) and cytochalasin D triggered proMMP-2 activation and cell death in U87 glioma cells. ConA decreased G6PT gene expression, an event that was also observed in cells overexpressing the full-length recombinant MT1-MMP protein. Overexpression of a membrane-bound catalytically active but cytoplasmic domain-deleted MT1-MMP was unable to downregulate G6PT gene expression or to trigger necrosis. Gene silencing of MT1-MMP with small interfering RNA prevented proMMP-2 activation and induced G6PT gene expression. ConA inhibited Akt phosphorylation, whereas overexpression of recombinant G6PT rescued the cells from ConA-induced proMMP-2 activation and increased Akt phosphorylation. Altogether, new functions of MT1-MMP in cell death signaling may be linked to those of G6PT. Our study indicates a molecular signaling axis regulating the invasive phenotype of brain tumor cells and highlights a new "bioswitch" function for G6PT in cell survival.

MT1-MMP down-regulates the glucose 6-phosphate transporter expression in marrow stromal cells: a molecular link between pro-MMP-2 activation, chemotaxis, and cell survival

Bone marrow-derived stromal cells (BMSC) are avidly recruited by experimental vascularizing tumors, which implies that they must respond to tumor-derived growth factor cues. In fact, BMSC chemotaxis and cell survival are regulated, in part, by the membrane type-1 matrix metalloproteinase (MT1-MMP), an MMP also involved in pro-MMP-2 activation and in degradation of the extracellular matrix (ECM). Given that impaired chemotaxis was recently observed in bone marrow cells isolated from a glucose 6-phosphate transporter-deficient (G6PT-/-) mouse model, we sought to investigate the potential MT1-MMP/G6PT signaling axis in BMSC. We show that MT1-MMP-mediated activation of pro-MMP-2 by concanavalin A (ConA) correlated with an increase in the sub-G1 cell cycle phase as well as with cell necrosis, indicative of a decrease in BMSC survival. BMSC isolated from Egr-1-/- mouse or MT1-MMP gene silencing in BMSC with small interfering RNA (siMT1-MMP) antagonized both the ConA-mediated activation of pro-MMP-2 and the induction of cell necrosis. Overexpression of recombinant full-length MT1-MMP triggered necrosis and this was signaled through the cytoplasmic domain of MT1-MMP. ConA inhibited both the gene and protein expression of G6PT, while overexpression of recombinant G6PT inhibited MT1-MMP-mediated pro-MMP-2 activation but could not rescue BMSC from ConA-induced cell necrosis. Cell chemotaxis in response to the tumorigenic growth factor sphingosine 1-phosphate was significantly abrogated in siMT1-MMP BMSC and in chlorogenic acid-treated BMSC. Altogether, we provide evidence for an MT1-MMP/G6PT signaling axis that regulates BMSC survival, ECM degradation, and mobilization. This may lead to optimized clinical applications that use BMSC as a platform for the systemic delivery of therapeutic or anti-cancer recombinant proteins in vivo.

Reduction of the spin-orbit splittings at the n = 28 shell closure

The N = 28 shell closure has been investigated via the 46Ar(d,p)47Ar transfer reaction in inverse kinematics. Energies and spectroscopic factors of the neutron p(3/2), p(1/2), and f(5/2) states in 47Ar were determined and compared to those of the 49Ca isotone. We deduced a reduction of the N = 28 gap by 330(90) keV and spin-orbit weakenings of approximately 10(2) and 45(10)% for the f and p states, respectively. Such large variations for the f and p spin-orbit splittings could be accounted for by the proton-neutron tensor force and by the density dependence of the spin-orbit interaction, respectively. This contrasts with the picture of the spin-orbit interaction as a surface term only.

Effect of tetrahydrobiopterin on selective endothelial dysfunction of epicardial porcine coronary arteries induced by cardiopulmonary bypass

BACKGROUND

We hypothesized that cardiopulmonary bypass induces a selective alteration of the coronary arterial endothelial cell signal transduction which could be explained by a state of depletion and/or decreased activity of endogenous tetrahydrobiopterin (BH(4)). The aim of this study was to assess the effects of cardiopulmonary bypass and BH(4) on the endothelial function of epicardial coronary arteries in a swine model of cardiopulmonary bypass.

METHODS

Swine underwent 90 min of cardiopulmonary bypass alone (N=19) or in association with a brief cardioplegic arrest with (N = 6) or without (N = 5) in vivo BH(4) administration, followed by a 60-min period following weaning from cardiopulmonary bypass and were compared to a control group (N = 7). Endothelium-dependent relaxations of epicardial coronary artery rings were studied using standard organ chamber experiments in the presence or absence of in vitro BH(4) or superoxide dismutase (SOD) and catalase.

RESULTS

Cardiopulmonary bypass caused a statistically significant reduction of endothelium-dependent relaxations to serotonin (p < 0.0001), bradykinin (p < 0.001), UK14304 (p < 0.0001) and calcium ionophore (p < 0.01) in epicardial porcine coronary arteries. In vitro and in vivo BH(4) supplementation improved endothelium-dependent relaxations to serotonin and bradykinin, which were left unchanged by SOD-catalase administration. Cardiopulmonary bypass was associated with a decrease in nitric oxide availability (p = 0.002) and increased oxidative stress (p < 0.001), which were both restored by in vivo BH(4) administration (p < 0.001).

CONCLUSION

Treatment with BH(4) improves the endothelial dysfunction of porcine epicardial coronary arteries, restores nitric oxide availability and reduces the oxidative stress associated with cardiopulmonary bypass.

Inhaled prostacyclin reduces cardiopulmonary bypass-induced pulmonary endothelial dysfunction via increased cyclic adenosine monophosphate levels

OBJECTIVE

Cardiopulmonary bypass triggers a systemic inflammatory response that alters pulmonary endothelial function, which can contribute to pulmonary hypertension. This study was designed to demonstrate that inhaled prostacyclin, a selective pulmonary vasodilator prostaglandin, prevents pulmonary arterial endothelial dysfunction induced by cardiopulmonary bypass.

METHODS

Three groups of Landrace swine were compared: control without cardiopulmonary bypass (control group); 90 minutes of normothermic cardiopulmonary bypass (bypass group); 90 minutes of cardiopulmonary bypass and treated with prostacyclin during cardiopulmonary bypass (continuous nebulization with continuous positive airway pressure until the end of the cardiopulmonary bypass; prostacyclin group). After 60 minutes of reperfusion, swine were put to death and pulmonary arteries harvested. After contraction to phenylephrine, endothelium-dependent relaxation to bradykinin and acetylcholine was studied in standard organ chamber experiments. The pulmonary artery intravascular cyclic adenosine monophosphate content was compared between the 3 groups (post-cardiopulmonary bypass).

RESULTS

There was a statistically significant improvement of the endothelium-dependent relaxation to bradykinin in the prostacyclin group when compared with the bypass group (P <.05). There was no statistically significant difference for endothelium-dependent relaxation to acetylcholine (P >.05) between the prostacyclin and the bypass groups. There was a statistically significant decrease in the cyclic adenosine monophosphate content and a statistically significant increase of the mean pulmonary artery pressure in the bypass group only (P <.05).

CONCLUSION

Prophylactic use of inhaled prostacyclin has a favorable impact on the pulmonary endothelial dysfunction induced by cardiopulmonary bypass associated with preservation of pulmonary intravascular cyclic adenosine monophosphate content and the pulmonary vascular tone.

Influence of intracoronary shunt size on coronary endothelial function during off-pump coronary artery bypass

OBJECTIVE

The insertion of intracoronary shunts during off-pump coronary artery bypass surgery may induce severe endothelial dysfunction in the target arteries. The purpose of this study was to determine the role of the ratio of the shunt diameter to the target artery diameter in the development of endothelial dysfunction and to develop guidelines for selecting the most appropriate shunt size.

METHODS

Nine swine (25 +/- 4 kg) were used for this study. Three ClearView shunts 3 mm, 2 mm, and 1.25 mm in diameter were inserted proximally to distally via 3 arteriotomies into the right coronary artery to obtain oversizing with the 3-mm shunt, undersizing with the 1.25-mm shunt, and a satisfying congruence with the 2-mm shunt. The shunts were left in place for 15 minutes, and the levels of bleeding were quantified. Coronary rings upstream and downstream from the arteriotomies were then harvested and placed in organ chambers to study endothelium-dependent relaxations to serotonin and bradykinin. Noninstrumented coronary arteries served as controls.

RESULTS

A decrease of endothelium-dependent relaxation occurred with the 3-mm shunts (P <.005), which were associated with an adequate hemostasis. A decrease of endotheliumdependent relaxation occurred with the 2-mm shunts (P <.05), which were associated with intermittent bleeding, and no significant decrease of endothelium-dependent relaxation occurred with 1.25-mm shunts (P >.05), which were associated with continuous bleeding.

CONCLUSIONS

Intracoronary shunts are associated with different disadvantages, depending on the mismatch to the target coronary artery, and whatever their size, shunts are not the ideal device for safely obtaining a satisfactory hemostasis. These results support our clinical attitude of the selective use of intracoronary shunts.

Interrupted coalescent nitinol clip versus continuous suture coronary anastomosis: a comparative endothelial function study

BACKGROUND

A new penetrating stapled anastomotic system using nitinol microclips (Coalescent Surgical U-Clip) has been developed to facilitate the construction of compliant interrupted sutures for minimally invasive and robotic surgery as well as for conventional procedures. The purpose of this study was to determine the effect of nitinol U-Clips used for coronary anastomosis in the development of endothelial dysfunction, compared with conventional running sutures.

METHODS

In a porcine model, both internal thoracic arteries were harvested, and the heart was removed. In a Krebs solution, 2 anastomoses were realized ex vivo between internal thoracic arteries and the left anterior descending artery. One was carried out with 12 Coalescent microclips, and the other used conventional running 7-0 polypropylene suture material (Prolene). Coronary rings on the anastomotic sites were then placed in organ chambers filled with oxygenated Krebs solution. Vascular reactivity studies were performed in standard organ chamber experiments. After the contraction of the coronary arteries in response to prostaglandin F2alpha, the endothelium-dependent relaxation response to bradykinin was studied. The other coronary arteries served as controls.

RESULTS

There was no statistically significant difference among the groups (P >.05) in the amplitude of the contraction response to KCl and prostaglandin F2alpha. There were no statistically significant differences in endothelium-dependent relaxation response to bradykinin between the nitinol microclip group and controls, between the suture group and controls, and between the nitinol microclip and suture groups.

CONCLUSIONS

Coalescent nitinol U-Clips used as anastomotic devices do not induce an endothelial dysfunction and allow a compliant anastomosis under satisfactory conditions.

Reduced mortality and strokes with off-pump coronary artery bypass grafting surgery in octogenarians

BACKGROUND

Off-pump coronary artery bypass surgery (OPCAB) has been revived and has gained popularity, although the exact subsets of patients who might benefit most from this technique are unknown. The aim of this retrospective study was to compare the results of coronary artery bypass grafting surgery (CABG) in octogenarians using cardiopulmonary bypass (CPB) or OPCAB techniques.

METHODS AND RESULTS

Over a 5-year period (1995-1999), 125 patients older than 80 years of age were operated for isolated myocardial revascularization (63 using CPB and 62 with OPCAB). There was no statistically significant difference in preoperative comorbidities between groups or in mean left ventricular ejection fraction (54.5+/-15.3% in the CPB group and 50.9+/-13.5% in the OPCAB group, respectively). The mean number of distal anastomosis per patient was 2.9 in CPB group and 2.6 in OPCAB group (P=ns). The majority of patients in both groups had unstable angina and were operated on an urgent basis. The operative mortality was 15.9% in the CPB group and 4.8% in the OPCAB group (P=0.04). There were 4 postoperative strokes (6.3%) in the CPB group and none (0%) in the OPCAB group (P=0.04). The percentage of patients transfused was 92.1% in the CPB group and 72.6% in the OPCAB group (P<0.01). Postoperative myocardial infarction occurred in 11.3% in the CPB group and 14.5% in the OPCAB group (P=NS). For all the parameters entered in the multivariate analysis with logistic regression model, the type of surgery (CPB or OPCAB) was an independent predictor of operative mortality and stroke (P=0.0375). The odds ratio (OR) indicates that operative mortality and stroke occur 4 times (OR=4.171) more often in CPB patients than in OPCAB patients. Follow-up showed no significant difference between the 2 groups in terms of cardiac events and mortality.

CONCLUSIONS

This retrospective study suggests a benefit of OPCAB in terms of operative mortality and stroke for octogenarian patients when compared with CPB in our institution.

[Extracorporeal circulation: an extraordinary tool that is not just for cardiac surgeons]

Extracorporeal circulation (ECC) is not only used for open heart surgery. There are also other surgical and medical applications. ECC can be used for encephalic arteries surgery to induce hypothermia and maximally protect the brain. Femoro-femoral ECC may be needful for urgent traumatologic surgery of the supra-aortic trunci. Intracranial aneurysm repair can occasionally necessitate deep hypothermia and circulatory arrest with ECC. Renal cell carcinomas may metastasize to the right atrium and surgery with ECC is mandatory for complete excision. Some reports in the literature mention use of ECC for hepatic surgery of intra-hepatic aneurysms. With acute peripheral ischemia, metabolites in the affected limb can be washed out with good results. Medical indications for ECC are numerous with pulmonary assistance as one of the foremost when mechanical ventilation failed. Homogeneous and rapid rewarming of hypothermic patients can be achieved with ECC. Finally, some groups have reported the use of ECC to administer chemotherapy in limb melanoma.

[Chronic constrictive pericarditis in African children: report of a case]

The chronic constrictive pericarditis is a rare affection, with multiple etiologies and concerning especially the adult. We report a case of chronic constrictive pericarditis in an African child in whom no etiology was found. A review of the literature raises the characteristics of chronic constrictive pericarditis for a better therapeutic management.

Analysis of the role of type 1 core O-glycans in the binding of anti-MUC1 antibodies by cytofluorometry and synthetic peptide/glycopeptide binding inhibition studies

A panel of 56 MAbs submitted to the ISOBM TD-4 (MUC1) Workshop were analysed in two systems. These systems were designed to screen for peptide type 1 core O-glycan-related reactivities. Using synthetic MUC1 mucin-related peptides and glycopeptides, the panel of MAbs were tested for relative binding affinities to type 1 core O-glycan-substituted MUC1 structures. These studies utilized a competitive binding format with a native human adenocarcinoma-derived mucin as a solid phase. This system allows for analysis of the type 1 core glycoform subspecificity of each MAb. The second approach taken in parallel, utilized MCF-7 (BrCa) and OVCAR (OVCa) cell lines which were grown in the presence or absence of phenyl-N-acetylgalactosaminide (p-gal), a blocker of mucin O-linked glycosylation. These cells were analysed by FACS to examine the role these same glycan substitutions play with regard to either the diagnostic or therapeutic application of these MAbs. By FACS analysis there was a consistent increased 'epitope exposure' for peptide-specific MAbs binding in the presence of p-gal. In addition, a single MAb (TD-4 #150) is interpreted to react with a type 1 core O-glycan, probably with Tn, TF or STn specificity.

Summary report on the ISOBM TD-4 Workshop: analysis of 56 monoclonal antibodies against the MUC1 mucin. San Diego, Calif., November 17-23, 1996

Sixteen research groups participated in the ISOBM TD-4 Workshop in which the reactivity and specificity of 56 monoclonal antibodies against the MUC1 mucin was investigated using a diverse panel of target antigens and MUC1 mucin-related synthetic peptides and glycopeptides. The majority of antibodies (34/56) defined epitopes located within the 20-amino acid tandem repeat sequence of the MUC1 mucin protein core. Of the remaining 22 antibodies, there was evidence for the involvement of carbohydrate residues in the epitopes for 16 antibodies. There was no obvious relationship between the type of immunogen and the specificity of each antibody. Synthetic peptides and glycopeptides were analyzed for their reactivity with each antibody either by assay of direct binding (e.g. by ELISA or BiaCore) or by determining the capacity of synthetic ligands to inhibit antibody binding interactions. There was good concordance between the research groups in identifying antibodies reactive with peptide epitopes within the MUC1 protein core. Epitope mapping tests were performed using the Pepscan analysis for antibody reactivity against overlapping synthetic peptides, and results were largely consistent between research groups. The dominant feature of epitopes within the MUC1 protein core was the presence, in full or part, of the hydrophilic sequence of PDTRAPAP. Carbohydrate epitopes were less easily characterized and the most useful reagents in this respect were defined oligosaccharides, rather than purified mucin preparations enriched in particular carbohydrate moieties. It was evident that carbohydrate residues were involved in many epitopes, by regulating epitope accessibility or masking determinants, or by stabilizing preferred conformations of peptide epitopes within the MUC1 protein core. Overall, the studies, highlight concordance between groups rather than exposing inconsistencies which gives added confidence to the results of analyses of the specificity of antimucin monoclonal antibodies.

Characterization of Cdk2-cyclin E complexes in plasma membrane and endosomes of liver parenchyma. Insulin-dependent regulation

Rat liver parenchyma Golgi/endosomes fractions harbor a tyrosine-phosphorylated 34-kDa protein. Screening of Golgi, endosomes (ENs), plasmalemma (PM), and cytosolic (Cyt) fractions revealed the presence of the mitotic kinase Cdk2 in ENs, PM, and Cyt. The fluid phase endocytic marker horseradish peroxidase gained access to the endosomal Cdk2, confirming its localization. Cdk2 was shown to be associated to cyclin E and was active in ENs and PM fractions. The administration of a single dose of insulin (1.5 microgram/100 g, body weight) induced a time-dependent activation of the insulin receptor kinase in these structures. Insulin receptor-kinase activation was followed by the inhibition of immunoprecipitated Cdk2-cyclin E kinase activity in PM and the progressive disappearance of cyclin E. In marked contrast, no such effect was observed in ENs. The injection of a phosphotyrosyl phosphatase inhibitor (bpV(phen)) increased the levels of cyclin E in ENs and PM. A massive recruitment of p27(kip1) was observed in the Cdk2-cyclin E complexes isolated from PM and Cyt but not from ENs. In vitro, Cdk2-cyclin E complexes have the capacity to inhibit the formation of hybrid structures containing horseradish peroxidase and radioiodinated epidermal growth factor. Therefore, in the PM and ENs of adult rat liver, an active and regulated pool of the mitotic kinase Cdk2-cyclin E and some yet to be defined effectors are present. Cdk2 may contribute to the modulation of transport events and/or maintenance of the topology of endocytic elements.

Compartmentalization of the mitogen-activated protein kinase (MAPK) in hepatic endosomes: association with the internalized epidermal growth factor (EGF) receptor

A pool of MAPK was found in hepatic plasma membrane (PM) and endosomes (ENs). After injection of a single dose of EGF (10 microg/100 g body weight), MAPK was detected in EGF receptor (EGFR) immunoprecipitates prepared from ENs. MAPK was detected in a time-dependent manner in EGFR immunoprecipitates that was coincident with the progressive concentration of the EGFR. The EGFR-associated MAPK was also detected by using an anti-phospho-MAPK suggesting that it was active. MAPK was present in wheat-germ agglutinin (WGA) eluates prepared from ENs and was maximally tyrosine-phosphorylated at the time peak of EGFR internalization. MAPK therefore is compartmentalized in PM and ENs of rat liver. A fraction of the endosomal MAPK was found to be associated with the internalized EGFR complexes, suggesting that it plays a role in the control of the EGFR activity at this locus.

Protein model determination from crystallographic data

Crystallographic studies play a major role in current efforts towards protein structure determination. However, despite recent advances in computational tools for molecular modeling and graphics, the task of constructing a model of the tertiary structure of a protein from experimental data remains complex and time-consuming, requiring extensive expert intervention. This paper describes an approach to protein model determination that incorporates crystallographic data, along with sequence data. A model is represented as an annotated graph that traces the backbone and side chains for a protein. The proposed approach incorporates numerical techniques that are applied to construct and analyze an electron density map for a unit cell of a crystal. The purpose of this work is to advance the ability to discern meaningful features of protein structure through the use of topological analysis of the relative density. Experimental results, which demonstrate the viability of the approach, are reported.

Protein model representation and construction

Crystallographic studies play a major role in current efforts towards protein structure determination. However, despite recent advances in computational tools for molecular modeling and graphics, the task of constructing a protein model from crystallographic data remains complex and time-consuming, requiring extensive expert intervention. This paper describes an approach to automating the process of model construction, where a model is represented as an annotated trace (or partial trace) of the three-dimensional backbone of the structure. Potential models are generated using an evolutionary algorithm, which incorporates multiple fitness functions tailored to different structural levels in the protein. Preliminary experimental results, which demonstrate the viability of the approach, are reported.

Analysis of Three-Dimensional Protein Images

A fundamental goal of research in molecular biology is to understand protein structure. Protein crystallography is currently the most successful method for determining the three-dimensional (3D) conformation of a protein, yet it remains labor intensive and relies on an expert's ability to derive and evaluate a protein scene model. In this paper, the problem of protein structure determination is formulated as an exercise in scene analysis. A computational methodology is presented in which a 3D image of a protein is segmented into a graph of critical points. Bayesian and certainty factor approaches are described and used to analyze critical point graphs and identify meaningful substructures, such as alpha-helices and beta-sheets. Results of applying the methodologies to protein images at low and medium resolution are reported. The research is related to approaches to representation, segmentation and classification in vision, as well as to top-down approaches to protein structure prediction.

Conformational analysis from crystallographic data using conceptual clustering

The rapid growth of crystallographic databases has created a demand for novel and efficient techniques for the analysis of molecular conformations, in order to derive new concepts and rules and to generate useful classifications of the available data. This paper presents a conceptual clustering approach, termed IMEM (image memory), which discovers the conformational diversity present in a dataset of crystal structures. In contrast to numerical clustering methods, IMEM views a molecular structure as comprising qualitative relationships among its parts, i.e. the structure is viewed as a molecular scene. In addition, IMEM does not require the user to have any a priori knowledge of an expected number of conformational classes within a given dataset. The IMEM approach is applied to several datasets derived from the Cambridge Structural Database and, in all cases, chemically correct and sensible conformational classifications were discovered. This is confirmed by a rigorous comparison of IMEM results with published conformational data obtained by energy-minimization and numerical clustering methods. Conformational analysis tools have an important part to play in the conversion of raw molecular databases to knowledge bases.