Registration of 3D CT and ultrasound datasets of the spine using bone structures

OBJECTIVE

In navigated orthopedic surgery, accurate registration of bones is of major interest. Usually, this registration is performed using landmarks positioned directly on the bone surface. These landmarks must be exposed during surgery. Our goal is to avoid the exposure of bone surface for the sole purpose of registration by using an intraoperative ultrasound device that can localize the bone through tissue.

METHOD

We propose an algorithm for the registration of CT and ultrasound datasets that takes into account the fact that ultrasound produces very noisy images (speckle) and shows only parts of the bone surface. This part is made from the CT dataset. Next, a surface volume registration is performed by searching for a position of the estimated surface that maximizes the average gray value of the voxels in the ultrasound dataset covered by the surface.

RESULTS

The algorithm was implemented and validated using an ex vivo preparation of a human lumbar spine with surrounding muscle tissue. On the basis of this data, the method has a large radius of convergence and a repeatability of 0.5 mm for displacement and 0.5 degrees for rotation.

CONCLUSIONS

A robust algorithm for the registration of 3D CT and ultrasound datasets is presented. The computation time seems sufficiently short to permit intraoperative use.

Therapy of metabolic disorders with intravenous (IV) access ports and long term intravenous L-carnitine therapy

With the expansion of newborn screening to include many organic acidurias and fatty acid oxidation defects, effective therapies of these disorders will be needed. Currently severe disorders such as methylmalonic and propionic aciduria. conventional therapy with diet and oral L-camitine often prove ineffective in preventing failure to thrive and recurrent metabolic decompensations. L-carnitine provides a natural pathway for removal of the toxic metabolites in these disorders and is life saving therapy but, with poor oral absorption (25%), it is difficult to supply adequate carnitine to meet the metabolic needs of these patients. Long term intravenous L-carnitine therapy, administered through a subcutaneous venous access port in 5 patients with organic acidurias [propionic aciduria (2), methylmalonic aciduria (2), 3 methylglutaconic aciduria(1)] resulted in improved growth, lower frequency of metabolic decompensations and increased tolerance of natural protein in the diet. An added benefit was the ability to initiate fluid. electrolytes, and antibiotics during metabolic decompensations at home thus averting hospitalizations.

[Pacemaker in therapy of heart failure--biventricular stimulation]

The management of congestive heart failure remains a therapeutic challenge despite recent advances in drug therapy, including ACE inhibitors, beta blockade and spironolacton treatment. Patients affected with the disease still have a restricted quality of life and a poor prognosis in the long run. Epidemiologically, the incidence and prevalence are increasing due to improved survival from both coronary artery disease and arterial hypertension. A subgroup of patients presents with marked prolongation of the QRS-complex in the surface ECG, mostly with a left bundle branch block pattern. This acts as a marker for interventricular conduction abnormality and specifically indicates a reduced left ventricular systolic function. Biventricular pacing tries to resynchronize the abnormal activation pattern by actively influencing diastolic filling and systolic function. The mechanisms involved are supposed to be restoration of left ventricular septal mechanical synchrony, reduction in presystolic mitral regurgitation and optimization of diastolic function with the maximization of diastolic filling time. In this article the current role and future directions of biventricular pacing are discussed.

Transvenous left ventricular lead implantation with the EASYTRAK lead system: the European experience

Several independent studies suggest that resynchronization therapy--achieved by left- or biventricular pacing--improves hemodynamics in heart failure patients with interventricular conduction disturbances. Delivery of this new therapy in an effective and minimally invasive manner presents technical challenges, as transvenous access to the left ventricle is required. Since 1999, a novel over-the-wire approach combining standard pacing lead and angioplasty technology has been evaluated in several European countries. This new left ventricular lead, the EASYTRAK system (Guidant, St. Paul, MN), has been clinically evaluated in 2 phases. The first phase was a clinical investigation to obtain the CE-mark (i.e. European Commission approval). The second phase, which started immediately after the CE-mark was obtained, consisted of a postmarket surveillance called the European registry. This article reports on the results of the pre-CE-mark clinical investigation and the preliminary results of the European registry (first 150 patients). During the pre-CE-mark clinical investigation of the EASYTRAK system, lead performance was assessed in 36 successfully implanted patients. The patients had indications for VVI-pacing, symptoms of heart failure and significant left ventricular dysfunction. The left ventricular lead was implanted in conjunction with a conventional right ventricular lead and a new heart failure device (CONTAK TR, Guidant, Brussels, Belgium). Lead measurements (threshold, sensing, and impedance) were performed at implant and subsequent follow-ups. The stimulation thresholds at 0.5 msec impulse width were acceptable, although (as expected) slightly higher than with standard right ventricular pacing leads: 1.39 +/- 1.15 V at implant, 1.72 +/- 1.26 V at predischarge, 1.54 +/- 0.88 V at 2 weeks, 1.38 +/- 0.80 V at 6 weeks, and 1.24 +/- 0.73 V at 12 weeks. R-wave and impedance measurements were stable over time. A revision of the EASYTRAK lead was required in 3 patients. No perforations were observed. During the second phase of the European registry, 150 implants were attempted in 63 centers from November 1999 to January 2000. The EASYTRAK was implanted with a pulse generator offering, in addition to resynchronization therapy, either tachycardia monitoring (CONTAK TR) or implantable cardioverter defibrillator therapy (CONTAK CD), depending on the patient indication. Over half of the centers involved had not previously implanted the EASYTRAK system. Total implant success rate was 83% (135/150), skin-to-skin duration of the implant was 169 +/- 81 minutes (range, 53-480 minutes), with a clear learning curve. Once the coronary sinus was found, the implant success rate was 92%. One lead dislodgment and 2 cases of phrenic nerve stimulation were reported. We conclude that the new EASYTRAK lead design for transvenous left ventricular lead implantation seems to be a suitable and safe tool for delivering resynchronization therapy to heart failure patients.

On the significance of telomerase activity in human malignant glioma cells

Telomerase is critical for tumor cell immortalization and is a novel target for cancer chemotherapy. Here, we examined whether telomerase is expressed in glioma cell lines, whether telomerase activity is regulated by bcl-2 or p53, and whether telomerase activity predicts response to chemotherapy. Further, we characterized the effects of a candidate telomerase inhibitor, penclomedine, in glioma cells. All 12 human malignant glioma cell lines examined were telomerase positive. Telomerase activity was not modulated during cell cycle progression, did not correlate with p53 status or bcl-2 family protein expression, and did not predict drug sensitivity, except for an association with resistance to carmustine. Ectopic bcl-2 expression did not enhance telomerase activity. Wild-type p53 reduced telomerase activity in cell lines retaining p53 activity but not in p53-mutant cell lines. Penclomedine killed glioma cells via an apoptotic, but death receptor-, bcl-2- and caspase-independent pathway, but did not inhibit telomerase and did not act synergistically with cytotoxic drugs. We conclude that telomerase activity does not account for the differential chemosensitivity of human glioma cells and that penclomedine kills glioma cells via a telomerase-independent pathway.

Glutathione S-transferase and drug sensitivity in malignant glioma

Malignant gliomas are largely resistant to current approaches of adjuvant chemotherapy. Gluthatione S-transferases (GST) have been attributed a role in the resistance of cancer cells, e.g., to nitrosoureas. Here, we assessed the expression levels of GST-pi and GST-mu RNA and protein as well as total GST activity in a panel of 12 human glioma cell lines and correlated these data with p53 status, BCL-2 family protein expression and drug sensitivity in these cells. Neither GST protein levels nor GST activity correlated with genetic or functional p53 status or with the expression of various BCL-2 family proteins. No evidence for GST-mediated protection from chemotherapeutic drugs became apparent. In contrast, high levels of GST-pi protein, probably the major source of GST activity in glioma cells, and of total GST activity correlated with enhanced sensitivity to vincristine-induced clonogenic cell death. Expression of GST-pi in human glioblastomas in vivo was confirmed by immunohistochemistry. Neither total, nor cytoplasmic or nuclear, GST-pi immunoreactivity correlated with the response to adjuvant radiotherapy or radiochemotherapy. A comparative analysis of primary and recurrent tumors showed that GST expression was not enhanced by radiochemotherapy in vivo. We conclude that GST does not account for the differential chemosensitivity of glioma cell lines in vitro and does not accumulate in glioma subpopulations that form recurrent tumors after radiochemotherapy in vivo.

Nuclear coactivator protein p100 is present in endoplasmic reticulum and lipid droplets of milk secreting cells

We have identified the p100 protein, previously known as a novel cellular coactivator, as a constituent of endoplasmic reticulum and cytosolic lipid droplets from milk secreting cells. Cytosolic lipid droplets of terminally differentiated mammary epithelial cells are secreted as milk lipid globules. However, milk lipid globules did not have detectable amounts of p100 protein. The p100 protein was found also in cytosol from lactating mammary gland, in storage lipid droplets from mouse adipocytes, and in endoplasmic reticulum from liver. Immunofluorescence microscopy of mammary epithelial cells confirmed the presence of p100 in non-nuclear regions of these cells. Partial sequence analysis of tryptic peptides from p100 from cow mammary gland showed extensive homology with the reported sequence of p100 determined from a human cDNA. Antibodies against a peptide synthesized to duplicate a sequence in human p100 recognized a protein of the size of p100 in cow, mouse and rat cell fractions.

Poly(ADP-ribose) polymerase-independent potentiation of nitrosourea cytotoxicity by 3-aminobenzamide in human malignant glioma cells

Poly(ADP-ribose) polymerase is a zinc-finger DNA-binding protein that detects specifically DNA strand breaks generated by genotoxic agents and is thought to be involved in DNA repair. Here, we examined the effects of 3-aminobenzamide, a poly(ADP-ribose) polymerase inhibitor, on the chemosensitivity of human malignant glioma cells. 3-Aminobenzamide selectively potentiated the cytotoxicity of the nitrosoureas, nimustine, carmustine and lomustine in 10 of 12 human malignant glioma cell lines. In contrast, 3-aminobenzamide did not modulate the cytotoxic effects of doxorubicine, teniposide, vincristine, camptothecin or cytarabine. The nitrosoureas did not induce poly(ADP-ribose) polymerase activity in the glioma cells. Ectopic expression of truncated poly(ADP-ribose) polymerase containing the poly(ADP-ribose) polymerase DNA-binding domain, which acts as a dominant-negative mutant, in LN-18 or LN-229 cells did not alter the 3-aminobenzamide effect on nitrosourea-mediated cytotoxicity. Thus, 3-aminobenzamide may target another nicotinamide adenine dinucleotide (NAD)-requiring enzyme, but not poly(ADP-ribose) polymerase, when enhancing nitrosourea cytotoxicity in human malignant glioma cells. Carmustine cytotoxicity was associated with a G2/M arrest. Coexposure to carmustine and 3-aminobenzamide overcame this G2/M arrest in T98G cells, which are sensitized to carmustine by 3-aminobenzamide, but not in U251MG cells, which are refractory to 3-aminobenzamide-mediated sensitization to carmustine. Thus, 3-aminobenzamide-mediated sensitization to carmustine cytotoxicity may result from interference with the stable G2/M arrest response to carmustine in human glioma cells.

Evidence for a constitutive, verapamil-sensitive, non-P-glycoprotein multidrug resistance phenotype in malignant glioma that is unaltered by radiochemotherapy in vivo

Human malignant gliomas are commonly resistant to chemotherapy. Here, we examined the role of the multidrug resistance (mdr) mechanism in the chemo-resistance of these tumors, using a twofold approach: (i) by assessing a possible mdr phenotype before and after chronic drug exposure of glioma cells in vitro, and (ii) by assessing the modulation of expression of the mdr-associated P-glycoprotein (Pgp) using radiotherapy and serial cycles of chemotherapy in human glioblastoma patients in vivo. T98G, and to a lesser degree, LN-229 human malignant glioma cells exhibit a constitutive mdr phenotype as determined by the modulation of dye transport and by the augmentation of chemosensitivity by the mdr antagonist, verapamil. Thus, coexposure to verapamil enhances the cytotoxicity of vincristine, doxorubicin and VM26 in T98G cells and that of vincristine in LN-229 cells. Chronic exposure of the cells to low concentrations of vincristine and doxorubicin, but not VM26, topotecan or BCNU, moderately enhances the mdr-like phenotype, as assessed by drug expulsion assays. However, chronic exposure to increasing drug concentrations does not significantly alter the sensitivity to the respective drugs. These data are consistent with a constitutive, but not drug-inducible, mdr-like drug resistance in glioma cells in vitro. Immunocytochemical analysis of human malignant gliomas in vivo reveals that Pgp expression is more abundant in endothelial cells within the gliomas, than in the glioma cells proper. Importantly, Pgp expression is unaltered by radiochemotherapy, assessed by comparative immunocytochemistry of glioma specimens obtained serially before and after radiochemotherapy. We conclude that (i) glioma cells exhibit constitutive mdr-like drug resistance that is not significantly altered by chronic drug exposure in vitro; (ii) endothelial cells may play an important role in Pgp-mediated drug resistance of gliomas in vivo; (iii) radiotherapy and repeated chemotherapy cycles do not modulate Pgp expression in human malignant gliomas in vivo; (iv) there is preliminary evidence for a non-Pgp, verapamil-sensitive drug transport activity in glioma cells.

Aetiology of childhood vision impairment, metropolitan Atlanta, 1991-93

Data from the population-based Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) were used to describe the underlying causes of vision impairment (VI; corrected visual acuity in the better eye of 20/70 or worse) in young children (n = 228) in metropolitan Atlanta in 1991-93. Children with VI were identified through record review at multiple educational and medical sources. Children were categorised as having isolated VI or multiple disabilities (i.e. VI plus one or more of four additional developmental disabilities) and as having low vision (visual acuity 20/70-20/400) or blindness (visual acuity worse than 20/400). Medical conditions abstracted from MADDSP sources were reviewed to determine the probable aetiology of a child's VI. Aetiologies were assigned to one of three developmental time periods: prenatal, perinatal, or postnatal. Prenatal aetiologies were identified in 43% of the children; 38% of the prenatal aetiologies were genetic. Perinatal aetiologies were found in 27% of the children. Postnatal aetiologies were rare. Prenatal aetiologies were more common in children with isolated VI; perinatal and postnatal aetiologies were more common in children with multiple disabilities. Children with prenatal aetiologies tended to have less severe vision loss than did children with perinatal or postnatal aetiologies. The distribution varied by birthweight, but did not differ significantly by sex or race.

[Affective, somatoform and anxiety disorders in Germany--initial results of an additional federal survey of "psychiatric disorders"]

BACKGROUND AND AIMS

The paper informs about methods and field survey procedures used in the German National Health Interview and Examination Survey--Mental Health Supplement (GHS-MHS)--and provides 12-month prevalence estimates of affective, anxiety and somatoform disorders in the general population. Such data have previously not been available for Germany on a nationwide level.

METHODS

Findings are based on a two-stage design: In the first stage all the 7124 participants of the German National Health Interview and Examination Survey (core survey) completed the Composite International Diagnostic-Screener (CIDS) for mental disorders. In the second stage 4181 probands (all screen-positive and a random sample of 50% of the screen-negative subjects) were interviewed with the full Composite International Diagnostic Interview (DIA-X-M-CIDI) by clinical interviewers. The overall response rate was 87.6%.

RESULTS

Affective (12-months prevalence estimate: 6.3%), anxiety (9%) and somatoform disorders (7.5%) are widespread in all age groups (18 to 65 years) of the German population; women are significantly more often affected than men. The prevalence rates of somatoform and affective disorders were found to be significantly lower in the former East German Länder as compared to the former West, whereas no such difference was found with regard to anxiety disorders. All disorders resulted in considerable reduction of work productivity during the past month; affective disorders reported on average 1.3 days/month total impairment and 7.2 days/month partial impairment, indicated significantly higher reduction in work productivity than anxiety and somatoform disorders.

CONCLUSIONS

Affective, somatoform and anxiety disorders are highly prevalent mental disorders (total: 17.3%) in the German population. The result of a lower morbidity of affective and somatoform disorders in former East Germany was unexpected and requires further clarification. The findings on impairment of work productivity emphasize the economic impact of psychiatric disorders on society.

[Effect of hyperphosphorylation on structure of TAU protein]

Effect of hyperphosphorylation on structural properties and conformational stability of tau-protein was investigated by methods of circular dichroism and fluorescence decay. The normal protein displayed an unusual secondary structural elements--an extended left-handed helix. It is suggested that the structure of the normal tau-protein includes a globular C-terminal part with rigid extended tail, i.e., it is of a "tadpole" type. The normal protein structure is practically unaffected by changes in pH values. Hyperphosphorylation leads to some perturbation within the extended part of the protein molecule. Decrease in pH transforms the globular part of the hyperphosphorylated protein into the molten globule-like conformation.

Selective potentiation of drug cytotoxicity by NSAID in human glioma cells: the role of COX-1 and MRP

Here, we report that nonsteroidal anti-inflammatory drugs (NSAID) enhance the cytotoxic effects of doxorubicin and vincristine in T98G human malignant glioma cells. The cytotoxicity of BCNU, cisplatin, VM26, camptothecin, and cytarabine is unaffected by NSAID. No free radical formation is induced by doxorubicin or vincristine in the absence or presence of NSAID. Doxorubicin and vincristine cytotoxicity in the absence or presence of NSAID are unaffected by free radical scavengers. Functional inhibitors of phospholipase A2 (PLA2), such as dexamethasone and quinacrine, do not mimick the effects of NSAID. T98G cells, but not LN-18, LN-229, LN-308, or A172 glioma cells, express cyclooxygenase (COX-1) and NSAID do not modulate drug cytotoxicity in the other cell lines, except T98G. Thus, augmentation of doxorubicin and vincristine cytotoxicity by NSAID correlates with COX-1 expression. However, ectopic expression of COX-1 in LN-229 cells does not induce the phenotype of T98G cells, indicating that COX-1 inhibition does not mediate the effects of NSAID on drug cytotoxicity. In contrast, a multidrug resistance (MDR) phenotype due to expression of the multidrug resistance-associated protein (MRP) is most prominent in T98G cells and is amenable to modulation by indomethacin, suggesting that inhibition of MRP is at least in partly responsible for the potentiation of doxorubicin and vincristine cytotoxicity by NSAID.

Using at least 5x10(6)/kg CD34+ cells for autologous stem cell transplantation significantly reduces febrile complications and use of antibiotics after transplantation

For autologous stem cell transplantation, it is common practice to infuse at least 2 x 10(6)/kg CD34+ cells to ensure rapid engraftment. However it was recently claimed that increasing the threshold to 5 x 10(6)/kg leads to a faster platelet engraftment. To evaluate these threshold values in our patient population we undertook a retrospective analysis of 127 autologous transplants performed at our institution between 1992 and 1998. Diagnoses included Hodgkin's and non-Hodgkin's lymphoma, myeloma, acute leukaemias and solid tumours. The transplant was peripheral blood stem cells in 107 cases and CD34-selected peripheral blood stem cells in 20 cases. The median number of transplanted CD34+ cells was 3.2 x 10(6)/kg (range 0.64-25.9 x 10(6)/kg). Haematopoietic recovery to a neutrophil count >0.5 x 10(9)/l took a median of 10 (range 5-16) days from transplant. When comparing patients receiving at least 5 x 10(6)/kg and 2-5 x 10(6)/kg CD34+ cells we found a significant reduction in the median number of days with fever (1 vs 3.5 days, P = 0.0025), incidence of fever (78.8 vs 92.1%, P = 0.032) as well as duration of antibiotic treatment (7 vs 10 days, P = 0.038). This was paralleled by a faster neutrophil recovery to 0.5 x 10(9)/l (9 vs 10 days, P = 0.047). There was no significant difference in the number of platelet or red cell transfusions between the two groups. We conclude that transplantation with a stem cell dose of at least 5 x 10(6)/kg CD34+ cells reduces infectious complications and should thereby increase the safety of this type of therapy while reducing duration (and cost) of antibiotic therapy. The transplantation threshold should thus not remain at 2 x 10(6)/kg particularly in patients with a good stem cell mobilisation capacity.

Detection of the DeltaF508 mutation in the CFTR gene by means of time-resolved fluorescence methods

A rapid recognition in the base sequence of nucleic acids is an important prerequisite toward the diagnosis of genetic diseases and their carrier states. We have developed a hybridisation method in which a fluorescently labeled oligonucleotide is used to detect point mutations in a target by a simple fluorescence lifetime analysis of the emission of the fluorescent label. We applied this method to detect the deltaF508 mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene in a model system and with biologically derived PCR product and discuss the potential generality of this method.

Boswellic acids and malignant glioma: induction of apoptosis but no modulation of drug sensitivity

Steroids are essential for the control of oedema in human malignant glioma patients but may interfere with the efficacy of chemotherapy. Boswellic acids are phytotherapeutic anti-inflammatory agents that may be alternative drugs to corticosteroids in the treatment of cerebral oedema. Here, we report that boswellic acids are cytotoxic to malignant glioma cells at low micromolar concentrations. In-situ DNA end labelling and electron microscopy reveal that boswellic acids induce apoptosis. Boswellic acid-induced apoptosis requires protein, but not RNA synthesis, and is neither associated with free radical formation nor blocked by free radical scavengers. The levels of BAX and BCL-2 proteins remain unaltered during boswellic acid-induced apoptosis. p21 expression is induced by boswellic acids via a p53-independent pathway. Ectopic expression of wild-type p53 also induces p21, and facilitates boswellic acid-induced apoptosis. However, targeted disruption of the p21 genes in colon carcinoma cells enhances rather than decreases boswellic acid toxicity. Ectopic expression of neither BCL-2 nor the caspase inhibitor, CRM-A, is protective. In contrast to steroids, subtoxic concentrations of boswellic acids do not interfere with cancer drug toxicity of glioma cells in acute cytotoxicity or clonogenic cell death assays. Also, in contrast to steroids, boswellic acids synergize with the cytotoxic cytokine, CD95 ligand, in inducing glioma cell apoptosis. This effect is probably mediated by inhibition of RNA synthesis and is not associated with changes of CD95 expression at the cell surface. Further studies in laboratory animals and in human patients are required to determine whether boswellic acids may be a useful adjunct to the medical management of human malignant glioma.

Glutathione depletion and neuronal cell death: the role of reactive oxygen intermediates and mitochondrial function

Glutathione (GSH) levels are supposed to determine the vulnerability of many cells towards a wide array of insults. We investigated the effects of chronic inhibition of GSH synthesis and acute depletion of GSH on cerebellar granule neurons in vitro and determined cytoplasmic and mitochondrial GSH with relation to mitochondrial function and generation of reactive oxygen intermediates (ROI). l-buthionine sulfoximine (BSO), which irreversibly blocks gamma-glutamyl-cysteine synthase, led to a time- and concentration-dependent loss of cytoplasmic GSH, while mitochondrial GSH was relatively preserved. No increased generation of ROI was detected over 48 h and the mitochondrial membrane potential was largely maintained. Neuronal degeneration occurred when mitochondrial GSH levels had fallen below 50% of control after 24-36 h. In contrast, direct conjugation of mitochondrial and cytoplasmic GSH with etacrynic acid (EA), resulted in immediate loss of mitochondrial GSH, a large increase of ROI within 2 h, subsequent collapse of the mitochondrial membrane potential and complete cell death within 4-8 h. Electron microscopy studies revealed an as yet unknown change of the chromatin structure to a homogeneous granular pattern after BSO, while EA resulted in typical necrotic changes. No typical features of apoptosis, i.e., no chromatin condensation or DNA fragmentation were detected after GSH depletion after BSO or EA treatment.

First Report of East African Cassava Mosaic Begomovirus in Nigeria

Cassava (Manihot esculenta Crantz) is an important food crop in sub-Saharan Africa. One of the major production constraints is cassava mosaic disease caused by African cassava mosaic (ACMV) and East African cassava mosaic (EACMV) begomoviruses. ACMV is widespread in its distribution, occurring throughout West and Central Africa and in some eastern and southern African countries. In contrast, EACMV has been reported to occur mainly in more easterly areas, particularly in coastal Kenya and Tanzania, Malawi, and Madagascar. In 1997, a survey was conducted in Nigeria to determine the distribution of ACMV and its strains. Samples from 225 cassava plants showing mosaic symptoms were tested with ACMV monoclonal antibodies (MAbs) in triple antibody sandwich enzyme-linked immunosorbent assay (1). Three samples reacted strongly with MAbs that could detect both ACMV and EACMV. One of them did not react with ACMV-specific MAbs while the other two reacted weakly with such MAbs. With polymerase chain reaction (2), the presence of EACMV and a mixture of EACMV and ACMV in the respective samples was confirmed. These samples were collected from two villages: Ogbena in Kwara State and Akamkpa in Cross River State. Co-infection of some cassava varieties with ACMV and EACMV leads to severe symptoms. More importantly, a strain of mosaic geminivirus known as Uganda variant arose from recombination between the two viruses (2). This report provides evidence for the presence of EACMV in West Africa. References: (1) J. E. Thomas et al. J. Gen. Virol. 67:2739, 1986. (2) X. Zhou et al. J. Gen. Virol. 78:2101, 1997.

Flt3 ligand can promote survival and macrophage development without proliferation in myeloid progenitor cells

Flt3 ligand elicits a variety of effects on early hemopoietic progenitors by occupying its cognate receptor, Flt3, a member of the type III tyrosine kinase receptor family. The cytokines macrophage colony-stimulating factor (M-CSF) and stem cell factor (SCF) bind to related members of this tyrosine kinase receptors family, c-fms and c-kit, respectively. The relative effects of the cytokines M-CSF, SCF, and Flt3L on the proliferation and development of the late myeloid progenitors granulocyte-macrophage colony-forming cells (GM-CFC) were investigated. Distinct biologic responses were stimulated by ligand binding to these different tyrosine kinase receptors in enriched GM-CFC. M-CSF stimulated GM-CFC to proliferate and develop into macrophages. SCF, on the other hand, stimulated GM-CFC to develop into neutrophils. Flt3 ligand had a relatively small proliferative effect on enriched GM-CFC compared to SCF and M-CSF and had no ability to either stimulate colony formation or synergize with these two cytokines in promoting DNA synthesis, colony formation, or expansion in liquid culture. Flt3 ligand, however, was capable of maintaining the clonogenic potential of GM-CFC and acted as an anti-apoptotic agent as assessed using the Annexin-V apoptosis assay. GM-CFC cultured in Flt3 ligand eventually formed macrophages and neutrophils in liquid culture. Labeling with the membrane-associated cell tracker dye PKH26 indicated that the majority of the enriched GM-CFC responded to Flt3 ligand by undergoing limited proliferation and macrophage development, whereas other cells survived but did not proliferate and differentiate into macrophages. Thus, Flt3 ligand promoted survival and stimulated development without proliferation in primary-enriched myeloid progenitor cells.

Molecular dynamics of labeled oligonucleotide probes used for the detection of point mutations in DNA

The fluorescent label BODIPY 576-589 linked to the 5-end of an oligonucleotide via alkyl chain linkers can be used as a probe to detect point mutations in DNA. We have employed fluorescence anisotropy decay and dynamic fluorescence resonance energy transfer (FRET) in order to investigate the molecular origin of the fluorescence lifetime aberrations of BODIPY in the presence of a mismatched base. The results show that both, an increased flexibility of the alcyl chain linker to the BODIPY molecule as well as relaxation of the secondary structure of the whole complex, contribute to the decreased fluorescence lifetimes reported previously.

Hyperphosphorylation induces structural modification of tau-protein

The effect of hyperphosphorylation on the structural properties and conformational stability of bovine tau-protein was studied by means of circular dichroism and fluorescence lifetime techniques. Normal protein contains unusual secondary structure elements: extended left-handed helices. The structure of this protein was assumed to be of a 'tadpole' type - a globular C-terminal part with a long and rigid tail included in the extended left-handed helix. Either a decrease or an increase of pH induced only minor changes of the normal tau-protein surface. Hyperphosphorylation affected the extended part of the protein molecule; the decrease of pH in this case induced considerable structural rearrangements, and the conformation of the C-terminal part of the protein molecule was transformed into a molten globule-like state.

The topoisomerase I inhibitors, camptothecin and beta-lapachone, induce apoptosis of human retinal pigment epithelial cells

The aim of the study was to determine whether the topoisomerase I inhibitors, camptothecin and beta-lapachone, are suitable agents for the adjuvant pharmacotherapy of proliferative vitreoretinopathy (PVR). The effects of the drugs on cultured human retinal pigment epithelial (RPE) cells were examined using growth assays, cytotoxicity assays, single cell agarose gel electrophoresis, in situ DNA end labeling and immunoblot analysis for apoptosis-regulatory proteins. Both agents killed RPE cells in a concentration-and time-dependent manner. Cell death was apoptotic as assessed by single cell agarose gel electrophoresis and in situ DNA end labeling. Camptothecin, but not beta-lapachone, induced accumulation of p53 and the major growth arrest-associated p53 response protein, p21. Both drugs enhanced expression of the proapoptotic BAX protein. Camptothecin, but not beta-lapachone, synergistically enhanced RPE cell apoptosis induced by the cytotoxic cytokine, CD95 ligand (CD95L). This effect was linked to camptothecin-induced inhibition of RNA synthesis. Atypical topoisomerase I inhibitors may be promising agents for the adjuvant pharmacotherapy of PVR. Experimental studies to assess possible ocular toxicity upon local administration and to confirm its therapeutic efficacy in an animal model of PVR are required.