Bienzyme sensors based on novel polymethylferrocenyl dendrimers

Amperometric bienzyme electrodes with horseradish peroxidase (HRP) and glucose oxidase (GOx) co-immobilized on polymethylferrocenyl dendrimers deposited onto platinum electrodes have been used for determination of the hydrogen peroxide produced by the oxidase during the enzymatic reaction. The redox dendrimers consist of flexible poly(propylenimine) dendrimer cores functionalised with octamethylferrocenyl units. The effects of dendrimer generation, the thickness of the dendrimer layer, substrate concentration, interferences, and reproducibility on the response of the sensors were investigated. The new bienzyme biosensors respond to substrate at work potential values between 200 and 50 mV (vs. SCE), have good sensitivity, and are resistant to interferences. Figure.

Arrays of arrays for high-throughput gene expression profiling

Gene expression profiling using DNA arrays is rapidly becoming an essential tool for research and drug discovery and may soon play a central role in disease diagnosis. Although it is possible to make significant discoveries on the basis of a relatively small number of expression profiles, the full potential of this technology is best realized through more extensive collections of expression measurements. The generation of large numbers of expression profiles can be a time-consuming and labor-intensive process with current one-at-a-time technology. We have developed the ability to obtain expression profiles in a highly parallel yet straightforward format using glass wafers that contain 49 individual high-density oligonucleotide arrays. This arrays of arrays concept is generalizable and can be adapted readily to other types of arrays, including spotted cDNA microarrays. It is also scalable for use with hundreds and even thousands of smaller arrays on a single piece of glass. Using the arrays of arrays approach and parallel preparation of hybridization samples in 96-well plates, we were able to determine the patterns of gene expression in 27 ovarian carcinomas and 4 normal ovarian tissue samples, along with a number of control samples, in a single experiment. This new approach significantly increases the ease, efficiency, and throughput of microarray-based experiments and makes possible new applications of expression profiling that are currently impractical.

Differentiation of nonmetastatic and metastatic rodent prostate tumors with high spectral and spatial resolution MRI

MR images can be acquired with high spectral and spatial resolution to precisely measure lineshapes of the water and fat resonances in each image voxel. Previous work suggests that the high-resolution spectral information can be used to improve image contrast, SNR, sensitivity to contrast agents and to physiologic and biochemical processes that affect local magnetic susceptibility gradients. The potential advantages of high-resolution spectroscopic imaging (SI) suggest that it might be useful for early detection and characterization of tumors. The present experiments evaluate the use of high-resolution SI to discriminate between metastatic and nonmetastatic rodent Dunning prostate tumors. SI datasets were obtained at 4.7 Tesla with an in-plane resolution of 350-500 micron in a single 1.0-mm slice, and 6-8 Hz spectral resolution, before and after i.v. injection of an iron oxide contrast agent. Images of water signal peak height in nonmetastatic tumors were smoother in the tumor interior than images of metastatic tumors (P <.004 by t-test) before contrast media injection. This difference was stronger in contrast-enhanced images (P <.0004). In addition, the boundary between the tumor and muscle was more clearly demarcated in nonmetastatic than metastatic tumors. Combinations of image texture, tumor edge morphology, and changes in T2* following contrast media injection improved discrimination between metastatic and nonmetastatic tumors. The data presented here do not demonstrate that effective discrimination between metastatic and nonmetastatic tumors depends on the use of high-resolution SI. However, the results suggest that SI and/or other MR methods that provide similar contrast might be used clinically for early and accurate detection of metastatic disease.

MRI measurements correctly predict the relative effects of tumor oxygenating agents on hypoxic fraction in rodent BA1112 tumors

PURPOSE

We evaluate whether magnetic resonance imaging (MRI) with blood oxygenation level-dependent (BOLD) contrast correctly predicts the relative effects of tumor-oxygenating agents on hypoxic fraction in BA1112 rhabdomyosarcomas in WAG/Rij rats.

METHODS AND MATERIALS

The response of ten tumors to carbogen (95% O(2)/5% CO(2)), a perfluorocarbon emulsion (PFC), and the combination of PFC + carbogen was studied with high spectral and spatial resolution MR imaging of the water resonance at 4.7 Tesla. Decreases in MR signal linewidth indicate increases in tumor blood oxygen levels.

RESULTS

Average MR signal linewidth was decreased 2.0% by carbogen, 2.5% by PFC + air, and 4.9% by PFC + carbogen. PFC + carbogen caused a larger linewidth decrease than either treatment alone (p < 0.04 by ANOVA). Maps of pixels responding to treatment indicate that combining PFC with carbogen significantly enlarges the area of the tumor in which oxygen levels are increased (p < 0.01 by ANOVA).

CONCLUSION

MRI predicts that PFC + carbogen will increase radiosensitivity more than either treatment alone; this agrees with the known effects of these treatments on hypoxic fraction. Utilizing MRI to choose the treatment that maximizes the size and extent of increases in tumor oxygenation could reduce hypoxic fraction.

Uptake of a superparamagnetic contrast agent imaged by MR with high spectral and spatial resolution

Conventional MRI implicitly treats the proton signal as a single, narrow Lorentzian. However, water signals in vivo are often in homogeneously broadened and have multiple resolvable components. These components represent discrete populations of water molecules within each pixel which are affected differently by physiology and contrast agents. Accurate measurement of each component of the water resonance can improve anatomic and functional MR images and provide insight into the structure and dynamics of subpixelar microenvironments. This report describes high spectral and spatial resolution (HiSS) MR imaging of rodent prostate tumors before and after injection of a superparamagnetic contrast agent. HiSS datasets were used to synthesize images in which intensity is proportional to peak height, peak frequency, and linewidth. These images showed anatomic features which were not clearly delineated in conventional T(2) and gradient echo images. HiSS images obtained after injection of the contrast agent showed T *(2) and T(1) changes which were not seen in conventional images. These changes are associated with microvessel density and permeability. The results suggest HiSS with superparamagnetic contrast agents has the potential to improve characterization of tumors.

Phylogenetic analysis of the 5' subterminal region of isolates of Leishmania RNA virus-1

Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus present in some Leishmania species. The virus genome consists of a 450-nucleotide, 5' untranslated region (UTR) followed by the coat gene and the RNA-dependent RNA polymerase (RDRP). It has been shown that the 5' end UTR of the genome promotes internal initiation of translation in an in-vitro assay, indicating the presence of an internal ribosomal entry site (IRES) element upstream of the coat gene. The nucleotide sequences of the 5' subterminal regions of six new isolates of LRV1, of different geographical origins, have now been determined. The RNA folding of the 5' subterminal region of LRV1 has been predicted, using a combination of thermodynamic parameters and folding constraints based on nucleotide substitutions. Furthermore, a putative pyrimidine-rich region (a feature unique to all IRES elements), which is complementary to the Leishmania 18S rRNA, has been identified. The significance and relevance of these findings in the context of the function of the 5' UTR of LRV1 as an IRES element are discussed.

Evaluation of hematopoietic progenitors in hematopoietic progenitor cell transplants. CD34+ dose effect in marrow recovery. Retrospective analysis in 38 patients

Our main goal was to evaluate the CD34+ dose in patients undergoing haemotopoietic stem celltransplantation and its results in terms of recovery of neutrophile and platelet counts, transfusion requirements, days of fever, antibiotic requirements and length of hospital stay. We studied 38 consecutive patients with haematological malignancies transplanted at our Department, from Feb. 96 through Sept. 98. The CD34+ cell quantification technique was standardized, using a modification of the ISAGHE 96 protocol. Patients were sorted into three groups according to the CD34+ count administered: a) between 3 and 5 x 10(6) cells/kg; b) between 5 and 10 x 10(6) cells/kg; c) > 10 x 10(6) CD34+ cells/kg. As a secondary end point, results were assessed according to the number of aphereses required to arrive at the target count of CD34+, separating those patients that required only 1 or 2 aphereses versus those requiring 3 or more. Finally, an analysis was made of the results of transplantation comparing the different sources of stem cells (PBSC versus PBSC + B.M.). The best results were obtained in the group with cells between 3 and 5 x 10(6) CD34+. No statistically significant advantages were found in the group with cells over 5. The supra-optimal dose of more 10 x 10(6) would yield no additional beneficial results, while they can imply a greater infusion of residual tumor cells. The number of aphereses had no impact on engraftment. Results obtained with PBSC transplants were better than those with BM+PBSC in terms of neutrophile and platelet recovery. The number of CD34+ cells remains the main element in stem cell transplantation to evaluate the haematopoietic recovery after engraftment. Minimum and optimum yields remain unclear. Centers should establish their own optimal dose based on local methodologies and outcomes, maximizing costs and benefits.

Cyclic anhydride ring opening reactions: theory and application

The development of a zero net shrinkage dental restorative material based upon a polymer-bioactive-glass composite requires a second-phase material that expands. This study details the mechanisms of organic cyclic anhydride ring expansion via hydrolysis. Six cyclic anhydrides were used to represent potential side groups, each of which could be an expanding phase or component. Maleic, 4META, tetrahydrophthalic, norbornene, itaconic, and succinic anhydrides were modeled using the Austin method (AM1), a semi-empirical molecular orbital method. The reaction pathways were determined for the anhydride ring opening reaction to form an acid for each case. The activation barriers (Ea) for the ring openings were found from the transition state geometries wherein only one imaginary eigen value in the vibration spectrum existed (a true saddle point). In each case the reaction pathway included the hydrogen bonding of a H2O molecule to the ring, weakening of the C-O bridging bonds of the ring, and, finally, the dissociation of the H2O, forming two carboxyl groups and opening the ring. The activation for the ring openings are +34.3, +36.9, +40.6, +43.1, +45.9, and +47.7 kcal/mol, respectively. The volumetric expansion of the anhydrides was estimated based upon the dilation of C-O-C atomic distances. The dimensional change was found to be 24.0%, 24.0%, 19.1%, 20.3%, 20.8%, and 17.9% for the anhydride rings, respectively. Finally, it was found that a linear correlation exists between the cyclic anhydride C-O asymmetric rocking (as-v) vibration and the activation energy (Ea) for hydrolysis to an acid. This may be used as an experimental indicator of a cyclic anhydride's activity.

The predominant elF4G-specific cleavage activity in poliovirus-infected HeLa cells is distinct from 2A protease

Human enteroviruses and rhinoviruses rapidly and selectively abolish translation from cellular mRNA upon infection of susceptible cells. Expression of the poliovirus 2A protease (PV 2Apro) is sufficient to cause host translation shutoff through cleavage of elF4G (formerly p220, elF4 gamma) either directly or indirectly through activation of a cellular factor. Evidence exists for both direct and indirect cleavage mechanisms; however, factors presumed to participate in an indirect mechanism have not yet been purified or defined. Here we show that the dominant elF4G cleavage activity in lysates from infected HeLa cells was separable from PV 2Apro by size exclusion chromatography. 2Apro separated into two peak fractions which contained activity which cleaved a peptide substrate derived from the poliovirus polyprotein. These peak 2Apro fractions did not cleave elF4G or an elF4G-derived peptide, as expected, due to the poor efficiency of direct cleavage reactions. Conversely, fractions which contained peak elF4G cleavage activity and only trace amounts of 2Apro efficiently cleaved a peptide substrate derived from the previously mapped elF4G cleavage site and also cleaved a peptide derived from the poliovirus 1D2A region. The dominant elF4G cleavage activity was highly purified through four chromatography steps and found to be devoid of all traces of 2Apro or its precursors. Quantitation of 2Apro from lysates of infected cells showed that during infections in HeLa cells, 2Apro does not reach molar excess over elF4G, as previously shown to be required for direct elF4G cleavage in vitro. Further, infection of HeLa cells in the presence of 2 mM guanidine-HCl, a potent inhibitor of viral RNA replication, suppressed accumulation of 2Apro and its precursor 2ABC below detectable levels but was unable to delay the onset of elF4G proteolysis in vivo. The elF4G cleavage activity was still easily detectable in in vitro assays using fractions from guanidine-treated cells. Thus, the data suggest that poliovirus utilizes two catalytic activities to ensure rapid cleavage of elF4G in vivo. Although it was not directly measurable here, 2Apro likely does cleave a portion of elF4G in cells. However, the data suggest that a cellular factor which can be activated by small quantities of 2Apro constitutes the bulk of the elF4G-specific cleavage activity in infected cells and is responsible for the rapid and efficient elF4G cleavage activity observed in vivo.

Pulmonary capillaritis: a possible histologic form of acute pulmonary allograft rejection

Acute rejection after lung transplantation occurs commonly and is usually characterized histologically by a perivascular mononuclear infiltrate. We report five cases of pulmonary capillaritis with a histologic appearance distinct from typical rejection, occurring in patients ranging in age from 18 to 45 years, with a variety of underlying diseases including alpha1 antitrypsin deficiency, pulmonary hypertension, cystic fibrosis, and rheumatoid arthritis. Four of the five patients had alveolar hemorrhage histologically, and two had frank hemoptysis. Time of onset ranged from 3 weeks to many months after transplantation. Three cases were fulminant, and there were two deaths. In only one case, with methicillin-resistant Staphylococcus aureus bronchitis, could infection be established. All were treated with intensification of immunosuppressive therapy. Plasmapheresis was carried out in two cases and coincided with temporary improvement, but its efficacy was questionable because of concurrent immunosuppressive therapy. Two had recurrent biopsy-proven acute rejection within 6 weeks of treatment, and one had recurrent severe pulmonary hemorrhage that abated with total lymphoid irradiation. Our experience suggests that pulmonary capillaritis in lung transplant recipients can be an acute, fatal illness with the potential for recurrence in the survivors. We speculate that it represents a form of acute vascular rejection. Early pathologic diagnosis and aggressive immunosuppressive therapy are recommended. Although a humoral component was not documented, the possible response to plasmapheresis requires continued evaluation.

Correlation of magnetic resonance and oxygen microelectrode measurements of carbogen-induced changes in tumor oxygenation

PURPOSE

The aim of this work was to test the hypothesis that decreases in the linewidth of magnetic resonance (MR) water signals in tumors caused by oxygenating treatments are due to increases in capillary and venous oxygen saturation of hemoglobin, which are tightly coupled to increases in extravascular oxygen tension (pO2). To establish this link, changes measured by MR were compared to changes in tissue pO2 measured directly by oxygen microelectrodes during carbogen (95% O2/5% CO2) inhalation.

METHODS AND MATERIALS

Mammary adenocarcinomas (R3230AC) in nine rats were imaged at 4.7 Tesla. T1-weighted (TR = 200 ms, flip angle = 45 degrees) spectroscopic images of the water resonance in a single slice through each tumor were acquired with spectral resolution of 3.9 Hz and bandwidth of +/-1000 Hz. In the same slices in these tumors, microelectrode measurements were made using a non-Clark style oxygen electrode with a 350-micron tip. MR and microelectrode measurements were made during alternating periods of air and carbogen inhalation.

RESULTS

Water resonance linewidth decreased significantly during carbogen-induced hyperoxia. Paired Student's t-test analysis of microelectrode data indicated that pO2 was significantly (p < 0.05) increased as a result of carbogen inhalation. MR and microelectrode data averaged over each tumor demonstrated that decreased MR water signal linewidth is strongly correlated (r = 0.92, p < 0.05) with increased tumor pO2 levels.

CONCLUSION

Although tumor oxygenating agents increase response to radiation in rodent tumors, clinical studies have shown only marginal effects on the radiosensitivity of human tumors. This may be, in part, because the effects of tumor oxygenating treatments are highly heterogeneous both within each tumor and among a population of tumors. The noninvasive, high-resolution MR methods that are validated by the present work could guide the design of new and more effective tumor oxygenating agents and optimize treatments for individual patients.

Return to work after lung transplantation

The social rehabilitation of lung transplant recipients becomes increasingly important as the results of lung transplantation improve. Although return-to-work (RTW) rates have been published for recipients of other organ transplants, no such data are available after lung transplantation. The purpose of this study was to determine what factors influence RTW after lung transplantation. Of 99 lung transplant recipients (43 single, 56 bilateral) surveyed from Denver, Colorado, (n = 49) and Toronto, Ontario, Canada (n = 50), 22% (n = 22) were employed, 38% (n = 38) were unemployed but medically able to work, 29% (n = 29) were medically disabled, and 10% (n = 10) had retired. The RTW rate for those medically able to work was 37% (22/60), and it was identical at each center (n = 11). Only Canadian lung transplant recipients (36%, 4/11) secured new jobs, whereas all Colorado lung transplant recipients returned to their previous employment (100%, 11/11). A stepwise discriminant analysis revealed that (1) pretransplantation employment, (2) a diagnosis of emphysema, cystic fibrosis, or primary pulmonary hypertension, (3) a self-report of being physically able to work, (4) greater functional improvement as measured by post-lung transplantation percent predicted forced vital capacity, and (5) post-lung transplantation 6-minute walk > 550 m positively influenced RTW. This analysis accurately profiled 82% of the employed and 76% of the unemployed recipients for an overall effectiveness of 79%. The findings of this study are that (1) a 37% employment rate for those physically able was comparable to other types of organ transplant recipients, (2) employment was not determined by the type of lung transplantation procedure (single or bilateral), and (3) social factors remain employment barriers for some recipients, but their absence did not guarantee a better employment rate.

[Epidemiological study of pediculosis capitis and scabies in schoolchildren from Antofagasta, Chile, 1995]

In order to contribute to a better knowledge of the pediculosis capitis and scabies during March-December 1995, 1122 primary schoolchildren under 14 years of age in the city-port of Antofagasta in northern Chile (20 degrees South lat.), were examined. A total of 285 (25.4%) were found to be infested with Pediculus humanus capitis and only 20 (1.8%) with Sarcoptes scabiei. In general the rates of infestation to both ectoparasitic diseases were higher in groups of younger schoolchildren, also higher in women than in men and in those groups with high indexes of crowding and ignorance of the transmission mechanism of pediculosis capitis and scabies.

Leishmania RNA viruses in Leishmania of the Viannia subgenus

Karyotype analysis of 69 strains of Leishmania belonging to three species of the Viannia subgenus originating from the southeastern and southwestern regions of Colombia revealed approximately 5.3-kb RNAs in four strains of L. braziliensis and also in the World Health Organization reference strain L. guyanensis IWHI/BR/78/M5313. The RNA element in this reference strain and in L. braziliensis strains isolated from cutaneous and mucosal lesions of four patients hybridized with RNA probes prepared from cDNA of the RNA virus present in L. guyanensis strain CUMC-1-1A (LRV1-1). These strains also contained an 80-kD protein that reacted with polyclonal antibody prepared against a recombinant fragment of the coat (capsid) protein of LRV1-1. In addition, another Colombian strain of L. braziliensis was found to contain an approximately 3.5-kb RNA that did not hybridize with LRV1-1 probes. Contrasting with the strains containing the 5.3-kb RNA, a total lysate of this strain did not contain material reactive with antiserum to the capsid protein fragment. All Leishmania containing LRV1-related viruses identified to date have originated in the Amazon River basin. Karyotype analyses and biological characterization of 17 clones obtained from the highly metastatic L. guyanensis strain 5313 revealed retention of the approximately 5.3 kb RNA in all clones and no segregation of the virus with the metastatic trait. The restricted distribution of LRV1-related viruses among some strains of L. braziliensis and L. guyanensis circulating in the Amazon River basin makes these elements potential epidemiologic markers.