Topoisomerase I stimulates SV40 T antigen-mediated DNA replication and inhibits T antigen's ability to unwind DNA at nonorigin sites

We have previously found that purified SV40 T antigen and topoisomerase I (topo I) bind to one another in vitro. In this report, we determined the effects of human topo I on T antigen-mediated DNA replication and investigated whether it altered T antigen's biochemical activities. Topo I stimulates DNA replication and especially increases the amounts of finished circular molecules. This protein had no effect on T antigen's ability to bind, distort, or unwind the origin of replication. However, unwinding of DNA by T antigen was strongly inhibited by topo I when it was initiated at sites other than the origin. We demonstrate that the presence of T antigen binding sites in DNA interfere with inhibition of unwinding by topo I. These results indicate that topo I may increase the specificity of unwinding by inhibiting the reaction at non-origin sites. Fragments of T antigen that bind to topo I abrogate topo I's inhibition of non-origin-dependent unwinding, indicating that topo I inhibits unwinding through a direct interaction with T antigen. We propose a model whereby T antigen and topo I function together at the origin to specifically unwind it and initiate DNA replication.

Effect of shape, size, and valency of multivalent mannosides on their binding properties to phytohemagglutinins

Clusters of di-, tri-, and tetra-antennary alpha-D-mannopyranosides were synthesized in good yields based on the coupling of amine-bearing mono- or trisaccharide [Man alpha(1 --> 6)[Man alpha(1 --> 3)]Man] haptens to poly-isocyanate or -isothiocyanate tethering cores. The relative binding properties of the resulting multivalent ligands were determined by turbidimetric and solid phase enzyme-linked lectin assays (ELLA) using plant lectins (phytohemagglutinins) Concanavalin A (Con A) and Pisum sativum (pea lectin) having four and two carbohydrate binding sites, respectively. Rapid and efficient cross-linking between tetravalent Con A and mannopyranosylated clusters were measured by a microtiter plate version of turbidimetric analyses. In inhibition of binding of the lectins to yeast mannan, the best tetravalent monosaccharide (30) and trisaccharide (31) inhibitors were shown to be 140 and 1155 times more potent inhibitors than monomeric methyl alpha-D-mannopyranoside against pea lectin and Con A, respectively. Compounds 30 and 31 were thus 35- and 289-fold more potent than the reference monosaccharide based on their hapten contents. As a general observation, the ligands bearing the Man alpha(1 --> 6)[Man alpha(1 --> 3)]Man trimannoside structures were found to be more potent inhibitors for Con A than the ligands having single mannoside residues, whereas pea lectin could not discriminate between the two types of ligands.

Measurement of magnetization transfer in different stages of neurocysticercosis

The purpose of this study was to establish magnetization transfer ratio (MTR) in different stages of neurocysticercosis. A total 2,532 cysticerci were studied prospectively in 15 cases. MTR from different regions of the lesions (ie, the cyst, the protoscolex or mural nodule, the granuloma wall) were calculated in different stages of evolution/degeneration in all cases. Of a total 2,532 lesions studied, 2,261 (89.29%) were seen on routine spin-echo (SE) imaging. The rest of the lesions were only seen on magnetization transfer (MT) SE imaging. Maximum MTR was calculated from healing lesions (mean + SD = 31.0+/-2.8) and from the core of SE invisible lesions (30.0+/-5.1). Innocuous cystic lesions, which were hyperintense on T2-weighted images, did not show any MT (MTR = 5.10+/-1.2), whereas degenerating T2 hyperintense lesions showed MTR of 26.40+/-2.7. Nondegenerating and degenerating scolices showed an intermediate MTR of 21.7+/-3.3 and 15.0+/-4.5, respectively. MT varies between different parts of the lesion and also from the same part in different stages of evolution/degeneration of the lesion. The visibility of a lesion on MT-SE sequence was dependent on its MTR and its location at a particular site (cortical gray matter, white matter, or deep gray matter). The difference in MTR of the lesion and the surrounding brain parenchyma decides the resulting contrast and visibility of the lesion.

Role of presensitization and donor-recipient crossmatching in corneal graft outcome

PURPOSE

A positive donor-recipient crossmatch (CM) due to preexisting recipient lymphocytotoxic antibodies is known to be an important factor in allograft failure in the majority of organ transplantations. However, the effect of positive CM on corneal graft outcome is less known.

METHOD

Between 1982 and 1994, CM was performed by the microlymphocytotoxicity method using donor lymphocytes and recipient pretransplant serum in 759 consecutive corneal transplantations (maximal follow-up, 36 months). Patients were evaluated regarding the type of allospecificity of antibodies involved and their role on corneal graft outcome (rejection and failure).

RESULTS

A positive CM was found in 61 patients (8%) and a negative CM in 698 patients (92%). The positive and negative CM groups had similar graft rejection rates at 36 months. Patients with a positive CM due to antibodies directed against donor human leukocyte antigen (HLA) (as defined on the basis of private and public or CREG HLA allele specificities) did not have an increased risk of rejection. However, patients with positive CM and presensitization (previous graft or rejection history) had a statistically significant increase in risk of corneal endothelial rejection.

CONCLUSION

This study shows that donor-recipient CM could be a useful procedure for the selection of recipients for corneal transplantation in patients presensitized by anterior graft or previous corneal rejection.

Communication with chaotic lasers

Recent experiments with chaotic electronic circuits have shown the possibility of communication with chaos. The experimental demonstration of chaotic communication with an optical system is described. An erbium-doped fiber ring laser (EDFRL) was used to produce chaotic light with a wavelength of 1.53 micrometers. A small 10-megahertz message was embedded in the larger chaotic carrier and transmitted to a receiver system where the message was recovered from the chaos. Chaotic optical waveforms can thus be used to communicate masked information at high bandwidths.

High temperature conjugation of proteins with carbohydrates

A new procedure was used to conjugate lactose and dextran with BSA without using coupling or activating reagents. The method is simple, rapid and cheap. Reducing sugars covalently bind to proteins when lyophilized together and briefly heated to a high temperature.

Monitoring of cytomegalovirus infections by the CD8+CD38+ T-cell subset in kidney transplant recipients

BACKGROUND

The CD8+CD38+ T-cell subset can predict progression to acquired immune deficiency syndrome among human immunodeficiency virus-positive subjects. This T-cell subset usually increases during other active viral infections (cytomegalovirus [CMV], Epstein Barr virus). We report on its usefulness in the early detection of CMV infection in kidney transplant recipients.

METHODS

Quantitation of CD8+CD38+ T cells was monitored by dual-color flow cytometry analysis on 77 patients during the posttransplantation period. Seventeen of the 52 patients at risk for CMV disease (33%) had primary infection or reactivation and three patients had herpes simplex virus infection only.

RESULTS

In every patient with CMV disease, high values for the CD8+CD38+ subset were detected with a 90% positive predictive value for the primary infections. Elevated values were observed at the very first clinical signs of the viral disease or within the few preceeding days. Acute rejection episodes did not provoke false-positive results.

CONCLUSION

This immunologic marker is sensitive and easily obtainable on a daily basis. It may help to direct therapy during rejection or serve as a tool for early detection of clinical viral diseases.

Specific interaction of wild-type and truncated mouse N-methylpurine-DNA glycosylase with ethenoadenine-containing DNA

N-Methylpurine-DNA glycosylase (MPG), a ubiquitous DNA repair enzyme, is responsible for the removal of a wide variety of alkylated base lesions in DNA, e.g., N-alkylpurines and cyclic ethenoadducts of adenine, guanine, and cytosine. These lesions, some of which are mutagenic and toxic, are generated endogenously or by genotoxic agents such as N-alkylnitrosamines and vinyl chloride. Wild-type mouse MPG, expressed from recombinant baculovirus, was purified to near homogeneity for studying its specific interaction with substrate, 1,N6-ethenoadenine- (epsilonA-) containing DNA. Electrophoretic mobility shift assays (EMSA) indicated that MPG formed a specific complex with a 50-mer epsilonA-containing duplex oligonucleotide. This complex was shown to be a transient reaction intermediate, because it could be formed only with the unreacted substrate and contained active enzyme molecules. DNA footprinting studies confirmed the specific binding of the protein to the epsilonA-containing duplex oligonucleotide; eight nucleotides on the epsilonA-containing strand and 16-17 nucleotides in the complementary strand spanning the base adduct were protected from DNase I digestion. A systematic deletion analysis of MPG was carried out in order to determine the minimally sized polypeptide capable of forming a stable substrate complex that is also suitable for characterization by NMR spectroscopy and X-ray crystallography. A truncated polypeptide (NDelta100CDelta18) lacking 100 and 18 amino acid residues from the amino and carboxyl termini, respectively, was found to be the minimal size that retained activity. The truncated and wild-type enzymes have similar kinetic properties. Moreover, both EMSA and DNase I footprinting studies indicated identical pattern of specific binding by the truncated and full-length polypeptides. Removal of five and nine additional residues from the amino- and carboxyl-termini of this polypeptide, respectively, resulted in a complete loss of activity. These results suggest that minimal structural change occured as a result of truncation in the NDelta100CDelta18 mutant, which may thus be suitable for elucidating the structure and mechanism of MPG.

1H magnetic resonance imaging and 31P magnetic resonance spectroscopy in experimental filariasis

1H Magnetic resonance imaging and 31P magnetic resonance spectroscopy (MRS) have been carried out in experimental rodent filariasis, i.e., Acanthocheilonema viteae infection in the rodent host, Mastomys coucha. The T2-weighted image of the infected host shows fine hyperintense thread like structures of adult filariid nests in the cervical region. 31P MRS of normal and infected hosts, localized over the same region of interest, show seven major peaks corresponding to phosphomonoesters (including glucose-6-phosphate, fructose-6-phosphate, fructose-1-6-diphosphate, phosphorylcholine, and adenine monophosphate or AMP), inorganic phosphate, glycerophosphorylcholine, phosphoenolpyruvate, phosphocreatine and nucleoside di- and tri-phosphates. Concentrations of phosphomonoesters (PMEs) are higher in the normal rodent compared with the infected ones. In vivo 31P MRS provides a non-invasive assessment of tissue bioenergetics and phospholipid metabolism.

Role of in vivo proton magnetic resonance spectroscopy in the diagnosis and management of brain abscesses

OBJECTIVE

In vivo proton magnetic resonance spectroscopy was performed for 24 patients with pyogenic brain abscesses, to examine the consistency of the spectral patterns and to observe the changes in metabolites with treatment.

METHODS

Localized proton spectra were obtained from 4- to 8-ml volumes in the abscesses, using stimulated echo acquisition mode and spin echo sequences. Twenty-two patients were treated with combined surgical and medical therapy, and two patients were treated conservatively. High-resolution magnetic resonance spectroscopy was performed for 15 samples of abscesses obtained from these patients, to confirm the assignments of resonances seen in vivo. Postaspiration studies were performed for 12 patients treated with combined medical and surgical therapy and 2 patients treated medically.

RESULTS

Lactate and amino acids were seen in spectra for all patients, irrespective of the time of spectroscopy after the onset of combined medical and surgical therapy. Acetate and pyruvate disappeared after 1 week of combined treatment.

CONCLUSION

It was concluded that spectral patterns for brain abscesses are consistent and specific and can assist in the noninvasive diagnosis of abscesses. Responses to combined treatment could be monitored by showing the changes in metabolite patterns in serial spectroscopic studies.

Seasonal dynamics of the tissue levels of total protein, free amino acid and ribonucleic acid in an Indian air-breathing teleost, Channa punctatus

The tropical freshwater air-breathing teleost, Channa punctatus, reveals a seasonal metabolic reorganization with reference to its biochemical tissue compositions. The summer-adapted and winter-adapted C. punctatus seem to be two biochemically distinct populations. Besides, the different reproductive phases viz. prespawning, spawning, post-spawning, preparatory-I and preparatory-II are also biochemically distinct.

Chemoenzymatic synthesis of dendritic sialyl Lewis(x)

Traditional structure activity relationship studies (SAR) have led to the development of numerous sialyl Lewis(x) analogs in the search for potential antiinflammatory agents. However, these methods do not take into account cluster or multivalent effects. Reported herein is the chemoenzymatic synthesis of di-, tetra-, and octa-valent sLe(x) ligands scaffolded on dendrimers. Hypervalent L-lysine cores with covalently attached 2-acetamido-2-deoxy-D-glucose (N-acetylglucosamine, GlcNAc) residues were chemically prepared and enzymatically transformed into sLe(x) containing dendrimers so that multivalency, and its role in selectin-sLe(x) interactions may be evaluated. This work constitutes another successful enzymatic synthesis of sLe(x) and represents the first example of GlcNAc elongation on a synthetic dendrimer scaffold. These sLe(x) dendrimers are currently being investigated as selectin antagonists.

Infrared fluorescent detection of D1S80 alleles from blood and body fluid collected on IsoCode devices

A genetic locus D1S80 (pMCT 118) containing variable number of tandem repeats (VNTR) has been used extensively in forensic analysis and paternity testing. In the current research, DNA was isolated from blood saliva and nasal secretions collected on two types of IsoCode paper-based devices. The D1S80 locus was amplified using PCR technology, and the alleles were separated by gel electrophoresis and then detected using an infrared (IR) fluorescence automated DNA sequencer. IR-labeled amplification products were generated from human genomic DNA using oligonucleotide primers, which were covalently linked to an infrared fluorescent dye (IRD41) at the 5' end. This system combines IR fluorescence chemistry and laser technology, thus eliminating the need for post-electrophoretic gel handling for the detection of the alleles. Real-time detection after separation of the alleles is valuable for visualization of the data. The VNTR alleles are displayed as familiar autoradiogram-like images, which can also be analyzed by computer. Since DNA is eluted from the IsoCode devices only with sterile distilled water and without time-consuming methods of extraction, amplification can be performed from numerous samples within a short period of time.

Dexamethasone - Cyclophosphamide pulse (DCP) therapy in Pemphigus

Of the 37 patients enrolled for this treatment, 13 have been lost to follow up and 4 have died. Of the remaining 20, 8 are already in remission (40%), while 12 are still having active disease. Of the 8 patients who are now in remission, 1 is in phase II and taking monthly dexamethasone cyclophosphamide pulse and 50 mg cyclophosphamide daily while in 3 patients all the treatment has already been withdrawn (phase IV). All these patients are being followed up for any recurrence. The duration of remission has been more than 6 months in 7 patients (maximum 2 years). The chief side-effect observed was increased susceptibility to pyogenic and candidal infections of the skin and oral mucosa respectively. The other side-effects noted were generalized weakness and lethargy following DCP (1), irregular menstrual periods (1), amenorrhoea (1), general darkening of complexion (1), steroid psychosis (1), transient eosinophilia (1) and marked transient oligospermia.

Acrokerato - elastoidosis of costa: Report of three cases

Three cases of acrokeratoelastoidosis of Costa are reported. All the patients were females with marginal keratodermas composed of cornified papules, some of which were umbilicated, distributed along the borders of the hands and feet. A positive family history was present in all the cases.

Synthesis and biological properties of mannosylated starburst poly(amidoamine) dendrimers

Starburst PAMAM dendrimers ending with mannopyranoside residues were readily synthesized in large scale and good yields from commercially available dendrimers bearing high-density amine functionality on their surface and p-isothiocyanatophenyl 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranoside. The first four generations of this novel class of monodispersed neoglycoconjugates having up to 32 mannoside units were evaluated as ligands for the phytohemagglutinins from concanavalin A (Con A) and Pisum sativum (pea lectin) using enzyme-linked lectin assay (ELLA) and turbidimetric analyses. The binding properties of these glycodendrimers, together with reference monosaccharides, were determined using yeast mannan as a coating antigen and peroxidase-labeled lectins. These mannosylated dendrimers were demonstrated to be potent inhibitors with IC50 values 400 times better than those of monomeric methyl alpha-D-mannopyranoside taken as a standard. Their lipophilic character was shown to be sufficient for their direct use as coating antigens in microtiter plate assays. Moreover, their ability to bind and form insoluble carbohydrate-lectin complexes was also demonstrated by radial double immunodiffusion and turbidimetric analyses. Furthermore, the ability of these ligands to selectively precipitate a mannose-binding protein (Con A) from a crude lectin mixture was also demonstrated using polyacrylamide gel electrophoresis (SDS-PAGE). These multivalent neoglycoconjugates were shown to constitute novel biochromatography materials of high affinity for the easy isolation of carbohydrate-binding proteins.

Prevention by anti-LFA-1 of acute myoblast death following transplantation

Myoblast transplantation is a potential treatment for Duchenne muscular dystrophy. One of the problems possibly responsible for the limited success of clinical trials is the rapid death of the myoblasts after transplantation. To investigate this problem, myoblasts expressing beta-galactosidase were injected in the tibialis anterior muscles of mice. Beta-galactosidase activity was reduced by 74.7% after 3 days. Myoblast death observed at 3 days was reduced to 57.2% when the hosts were irradiated. This result suggested that host cells were contributing to this phenomenon. Transplantation in SCID and FK506-treated mice did not reduce cell death, indicating that mortality was not due to an acute specific reaction. In contrast, administration of the anti-LFA-1 (TIB-213) mAb markedly reduced myoblast death at 3 days without altering leukocyte tissue infiltration. We postulated that neutrophils were mediating myoblast mortality by an LFA-1-dependent mechanism. To test this hypothesis, IL-1beta-activated myoblasts were loaded with 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethylester) (DCFH), a marker for oxidative stress. Addition of neutrophils and zymosan-activated serum resulted in a time-dependent DCFH fluorescence; this neutrophil-induced oxidation was considerably inhibited by TIB-213. These results indicate that an effective control of the inflammatory reaction will be necessary for any new clinical trials of myoblast transplantation and suggest that neutrophil-mediated myoblast injury occurs by an LFA-1-dependent pathway.

MR imaging, MR angiography, and MR spectroscopy of the brain in eclampsia

PURPOSE

To compare the MR imaging and MR angiographic changes with in vivo proton MR spectroscopic findings and to determine the spectral differences between edema and ischemia in patients with eclampsia.

METHODS

Spin-echo MR imaging, MR angiography, and single-voxel proton MR spectroscopy were performed in 10 patients with eclampsia. MR studies were obtained within 3 to 5 days of diagnosis and repeated after 2 weeks with identical parameters.

RESULTS

Multifocal subcortical/cortical hyperintensities were noted in all 10 patients on T2-weighted images; in two patients, hyperintensities were seen in both cerebral hemispheres. In nine patients, MR angiograms showed narrowing of the major vessels constituting the circle of Willis that resolved after 2 weeks. In one patient with subtle imaging changes, MR angiography showed mild bilateral narrowing of the proximal middle and posterior cerebral arteries that did not change after 2 weeks, whereas imaging abnormalities worsened. Findings at single-voxel MR spectroscopy of the reversible T2 hyperintense lesions were significantly different from findings in the control group for N-acetylaspartate (NAA)/creatine ratios. One patient with mild abnormalities at MR imaging and MR angiography had lactate and decreased creatine and NAA, and on a follow-up study had a further decrease of NAA and creatine as well as a decrease in lactate.

CONCLUSION

In vivo proton MR spectroscopy may help to differentiate cerebral edema from ischemia in patients with eclampsia and thus may help to determine the prognosis for these patients.

Prevention by anti-LFA-1 of acute myoblast death following transplantation

Myoblast transplantation is a potential treatment for Duchenne muscular dystrophy. One of the problems possibly responsible for the limited success of clinical trials is the rapid death of the myoblasts after transplantation. To investigate this problem, myoblasts expressing beta-galactosidase were injected in the tibialis anterior muscles of mice. Beta-galactosidase activity was reduced by 74.7% after 3 days. Myoblast death observed at 3 days was reduced to 57.2% when the hosts were irradiated. This result suggested that host cells were contributing to this phenomenon. Transplantation in SCID and FK506-treated mice did not reduce cell death, indicating that mortality was not due to an acute specific reaction. In contrast, administration of the anti-LFA-1 (TIB-213) mAb markedly reduced myoblast death at 3 days without altering leukocyte tissue infiltration. We postulated that neutrophils were mediating myoblast mortality by an LFA-1-dependent mechanism. To test this hypothesis, IL-1beta-activated myoblasts were loaded with 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethylester) (DCFH), a marker for oxidative stress. Addition of neutrophils and zymosan-activated serum resulted in a time-dependent DCFH fluorescence; this neutrophil-induced oxidation was considerably inhibited by TIB-213. These results indicate that an effective control of the inflammatory reaction will be necessary for any new clinical trials of myoblast transplantation and suggest that neutrophil-mediated myoblast injury occurs by an LFA-1-dependent pathway.