Status and prospects of plant virus control through interference with vector transmission

Most plant viruses rely on vector organisms for their plant-to-plant spread. Although there are many different natural vectors, few plant virus-vector systems have been well studied. This review describes our current understanding of virus transmission by aphids, thrips, whiteflies, leafhoppers, planthoppers, treehoppers, mites, nematodes, and zoosporic endoparasites. Strategies for control of vectors by host resistance, chemicals, and integrated pest management are reviewed. Many gaps in the knowledge of the transmission mechanisms and a lack of available host resistance to vectors are evident. Advances in genome sequencing and molecular technologies will help to address these problems and will allow innovative control methods through interference with vector transmission. Improved knowledge of factors affecting pest and disease spread in different ecosystems for predictive modeling is also needed. Innovative control measures are urgently required because of the increased risks from vector-borne infections that arise from environmental change.

Multidisciplinary approach for in-deep assessment of joint prosthesis failure

In spite of advancement in biomaterials and biomechanics, in development of new osteo-integrative materials and coatings, and in macro- micro- component design, a non negligible fraction of the implanted prosthesis fails before the expected lifetime. A prospective observational clinical study has been conducted to define and apply a set of experimental techniques to in-deep assess the failure of joint prosthesis. Microbiological, histological and micro-structural techniques were implemented to specifically address phenomena occurring at the tissue-implant interface. Results obtained from 27 cases of prosthetic joint failure are discussed in terms of sensitivity and specificity. A procedural flow-chart is finally proposed for the assessment of joint prosthesis failure.

Different experimental protocols for decontamination affect the cleaning of medical devices. A preliminary electron microscopy analysis

The aim of the present study was to examine the efficiency of different decontamination-cleaning protocols on blood-soiled catheters used for interventional cardiology. Electrophysiology and cardiac ablation disposable devices were contaminated with bacteria-spiked human blood and underwent four different pre-sterilization protocols, including a chlorine-releasing agent, a polyphenolic emulsion, and an enzymatic detergent. Treated samples were examined by optical microscopy, scanning electron microscopy and transmission electron microscopy to identify and characterize biological and inorganic residuals. The use of chlorine as a first treatment caused denaturation of serum proteins and adherence of blood components to the surface of the device, thus hindering the cleaning efficiency of subsequent treatments with enzymatic detergents. An enzymatic/chlorine protocol was more efficient, but was considered to be a greater risk to healthcare staff. Polyphenolic-based treatments had the highest level of efficiency in bioburden removal, but interaction and adsorption of this class of chemicals onto biopolymers might lead to serious concerns about toxicity on subsequent reuse. Adequate pre-sterilization cleaning is fundamental for sterilization success and high-resolution electron microscopy can provide significant and detailed information about the efficiency of chemicals used for cleaning a blood-soiled device.

Experimental layout, data analysis, and thresholds in ELISA testing of maize for aphid-borne viruses

Several aspects of enzyme-linked immunosorbent assay (ELISA) procedures and data analysis have been examined in an attempt to find a rapid and reliable method for discriminating between 'positive' and 'negative' results when testing a large number of samples. A layout of ELISA plates was designed to reduce uncontrolled variation and to optimize the number of negative and positive controls. A transformation using the fourth root (A(1/4)) of the optical density readings corrected for the blank (A) stabilized the variance of most ELISA data examined. Transformed A values were used to calculate the true limits, at a set protection level, for false positive (C) and false negative (D). Methods are discussed to reduce the number of undifferentiated samples, i.e. the samples with response falling between C and D. The whole procedure was set up for use with an electronic spreadsheet. With the addition of few instructions of the type 'if em leader then em leader else' in the spreadsheet, the ELISA results were obtained in the simple trichotomous form 'negative/undefined/positive'. This allowed rapid analysis of more than 1100 maize samples testing for the presence of seven aphid-borne viruses-in fact almost 8000 ELISA samples.

Watermelon chlorotic stunt virus from the Sudan and Iran: Sequence Comparisons and Identification of a Whitefly-Transmission Determinant

ABSTRACT The genomes of two Watermelon chlorotic stunt virus (WmCSV) isolates, one from the Sudan and one from Iran, were cloned and sequenced. Sequence relationship with other geminiviruses characterizes WmCSV as a typical Eastern Hemisphere geminivirus with a bipartite genome. The two geographically distant WmCSV isolates from Africa and the Middle East share a very high overall sequence similarity: 98% between their DNA-A and 96% between their DNA-B components, and their respective capsid proteins are identical. A single amino acid change in the capsid protein (N131D) renders WmCSV whitefly nontransmissible. This region of the capsid is also implicated in transmission by Bemisia tabaci of Tomato yellow leaf curl virus.

Amino acids in the capsid protein of tomato yellow leaf curl virus that are crucial for systemic infection, particle formation, and insect transmission

A functional capsid protein (CP) is essential for host plant infection and insect transmission in monopartite geminiviruses. We studied two defective genomic DNAs of tomato yellow leaf curl virus (TYLCV), Sic and SicRcv. Sic, cloned from a field-infected tomato, was not infectious, whereas SicRcv, which spontaneously originated from Sic, was infectious but not whitefly transmissible. A single amino acid change in the CP was found to be responsible for restoring infectivity. When the amino acid sequences of the CPs of Sic and SicRcv were compared with that of a closely related wild-type virus (TYLCV-Sar), differences were found in the following positions: 129 (P in Sic and SicRcv, Q in Sar), 134 (Q in Sic and Sar, H in SicRcv) and 152 (E in Sic and SicRcv, D in Sar). We constructed TYLCV-Sar variants containing the eight possible amino acid combinations in those three positions and tested them for infectivity and transmissibility. QQD, QQE, QHD, and QHE had a wild-type phenotype, whereas PHD and PHE were infectious but nontransmissible. PQD and PQE mutants were not infectious; however, they replicated and accumulated CP, but not virions, in Nicotiana benthamiana leaf discs. The Q129P replacement is a nonconservative change, which may drastically alter the secondary structure of the CP and affect its ability to form the capsid. The additional Q134H change, however, appeared to compensate for the structural modification. Sequence comparisons among whitefly-transmitted geminiviruses in terms of the CP region studied showed that combinations other than QQD are present in several cases, but never with a P129.

Epidural spinal cavernous hemangioma

STUDY DESIGN

Five cases of epidural spinal cavernous hemangioma submitted to magnetic resonance imaging and surgery were reviewed.

OBJECTIVE

To correlate different magnetic resonance imaging appearances of epidural spinal cavernous hemangioma with histologic findings.

SUMMARY OF BACKGROUND DATA

Cavernous hemangioma is an uncommon vascular malformation that may occur anywhere in the central nervous system. Purely epidural lesions are very rare. Accurate correlation between magnetic resonance imaging appearances and histologic findings have not been reported in the literature.

METHODS

Five cases of epidural spinal cavernous hemangioma that had undergone magnetic resonance imaging evaluation followed by microsurgical removal, were retrospectively reviewed. Conventional spin-echo T1-, proton density- and T2-weighted magnetic resonance images were obtained in all cases, and gadolinium was used in all but one. Two cases have also been evaluated with computed tomography.

RESULTS

In two cases, magnetic resonance imaging showed mixed low- and high-signal intensity components in all sequences and pathologic examination showed degenerative phenomena and hemosiderin pigments. In the remaining three cases, magnetic resonance imaging showed low- or intermediate-signal intensity on T1-weighted and high-signal intensity on proton density- and T2-weighted images. In those cases, pathologic examination showed an absence of degenerative phenomena and no signs of hemorrhage. All patients underwent surgery by laminectomy and microsurgical resection. In all, significant improvement was obtained.

CONCLUSIONS

Epidural spinal cavernous hemangioma has a different magnetic resonance imaging appearance probably because of the presence or absence of the degenerative phenomena and hemosiderin pigments. As in cerebral locations, mixed signal intensity in all sequences on magnetic resonance images might be indicative of cavernous hemangioma. Presumptive preoperative diagnosis of the lesion may render the surgical approach less invasive.

Quantitation over time of tomato yellow leaf curl geminivirus DNA in its whitefly vector

ABSTRACT The amount of tomato yellow leaf curl geminivirus (TYLCV) DNA that accumulated in the vector Bemisia tabaci was studied by quantitative chemiluminescent dot-blot assay, using digoxigenin-labeled specific DNA probes. Large groups of female whiteflies were allowed to feed for 4, 12, 24, or 48 h on TYLCV-infected tomato plants and then were transferred to TYLCV-immune cucumber plants. Insects were sampled at different times during and after acquisition access and tested for TYLCV-DNA content. TYLCV-DNA assays were done either on whole insects oron the head plus prothorax (to include salivary glands) and abdomen separately. The maximum amount of TYLCV DNA, averaging from 0.5 to 1.6 ng per insect, was always attained at the end of the acquisition period. The mean amount then decreased by about 1 to 2% per day, remaining clearly detectable up to 20 days after the end of the acquisition period. Only some whiteflies that were TYLCV-positive in the abdomen were positive for head plus prothorax. In both parts of the body, TYLCV DNA remained detectable up to 18 days after the end of the acquisition period, showing that TYLCV DNA remains in insect tissues much longer than infectivity indicates.

Carbogen and nicotinamide combined with unconventional radiotherapy in glioblastoma multiforme: a new modality treatment

PURPOSE

A new radiotherapy schedule to treat glioblastoma multiforme after surgery, combining nicotinamide and carbogen.

METHODS AND MATERIALS

We analyzed 36 patients with glioblastoma multiforme treated after surgery with radiotherapy, Nicotinamide and Carbogen as follows: 7 patients were treated with accelerated fractionation: two fractions/day, 1.5 cGy/fraction, 6 h interval, 5 days/week, total dose 60 Gy in 4 weeks; 8 patients were treated with the same irradiation scheduling plus Nicotinamide at the dose of 4 g and 2 g in capsules, respectively, 1 h before the first and the second irradiation fraction; 21 patients were treated with accelerated radiotherapy, Nicotinamide, and Carbogen (inhaled 10 min before radiotherapy and during the whole course of irradiation). On the basis of surgical removal our patients were subdivided in three groups: totally resected, with residual tumor <50%, or >50%. Radiotherapy with accelerated fractionation was completed in the scheduled time without side effects on the whole group of patients and Carbogen inhalation did not cause significant change of cardiopulmonar parameters. The toxicity observed was predominant in the gastrointestinal tract and was related to Nicotinamide.

RESULTS

The median survival time (M.S.T.) was 10 months, as reported by others authors with conventional treatment, but in patients without surgical residual tumor and submitted to the complete treatment schedule, the survival at 35 months was around 25%.

CONCLUSIONS

We conclude that this method is feasible with acceptable toxicity; analyzing the survival curves appears to be a trend towards an improvement in survival in the subgroup of patients with gross total removal treated with the combination of Carbogen, Nicotinamide, and accelerated fractionation.

Quantitative determination of tomato yellow leaf curl geminivirus DNA by chemiluminescent assay using digoxigenin-labeled probes

A quantitative dot-blot hybridisation assay was developed for tomato yellow leaf curl geminivirus (TYLCV). The assay is based on chemiluminescent detection of viral and plasmid DNA using digoxigenin-labeled probes on nylon membranes. The response-error relationship was studied and a square root transformation was found to stabilise the variance of the response. An asymmetric sigmoid (gompertz) curve was used to describe the dose-response relationship. The detection limits and the precision profiles of the curves were studied. A method is suggested for setting an upper limit on the maximum DNA amount that can be discriminated from the upper asymptote. With respect to different times of exposure of an X-ray film to a membrane, the shortest times gave better upper limits and the longest times provided better detection limits. Purified virus and plasmid preparations were studied in various dilution media, such as TYLCV-free Bemisia tabaci (the whitefly vector) and tomato extracts, with particular attention to parallelism with standard calibration curves. Plasmid diluted in buffer was found useful for calibration of purified virus and virus in the vector, while extraction of known amounts of virus, in parallel with samples to be examined, was needed to quantify viral DNA in plant hosts.

Carbogen breathing in patients with glioblastoma multiforme submitted to radiotherapy. Assessment of gas exchange parameters

It has been reported that carbogen breathing yields a remarkable increase of radiosensitivity in murine tumour models. Hence, application of carbogen might be promising in radiotherapy of human tumours. We describe a method to increase arterial oxygenation and to ensure stability of O2 and CO2 during carbogen breathing in patients with malignant disease. We measured in 6 patients with histologically proven intracranial glioblastoma multiforme arterial blood gases, inspired and expired gas concentrations and vital signs either baseline and during carbogen breathing. The highest values of arterial oxygenation were achieved after 10 min of carbogen breathing and they remained stable up to 15 min. In none of our patients was N2 wash-out from the lungs completed in 15 min of carbogen breathing. In conclusion, carbogen breathing increased arterial oxygenation in patients with intracranial malignant diseases. The system used is reliable and of practical use. Monitoring of expired gas concentrations is highly recommended.

Long-term marrow culture in patients with aplastic anemia compared with marrow transplant recipients and normal controls

Patients with severe aplastic anemia (SAA; n = 46) were studied in long-term bone marrow culture (LTBMC) systems and compared with allogeneic marrow transplant (BMT) recipients (n = 16) (within 30 days following BMT) and normal control patients (n = 12). SAA patients were divided in two groups: transfusion-dependent (Tx-D) SAA patients (group A; n = 15) and transfusion-independent (Tx-I) patients after treatment with antilymphocyte globulin (group B; n = 31). Cultures were analyzed at three levels: stromal layer (SL) formation (score: 0, no SL; 1, half confluent SL; and 2, confluent SL), number of nucleated cells in suspension, and growth of CFU-GM colonies. SL formation was rapid and complete in SAA patients, groups A and B (mean score on day 14: 1.3 and 1.4), similar to controls (mean score on day 14: 1.3), whereas an impairment of SL formation was seen in BMT recipients (mean score on day 14: 1.0). The number of nucleated cells in suspension increased significantly on day 7 of culture in controls (7.6-fold), significantly more than in BMT and SAA patients, and declined thereafter. Colony formation was also significantly increased on day 7 in Tx-I SAA patients, BMT recipients, and normal controls (4-, 5-, and 16-fold, respectively), lasting respectively 2, 3, and 4 weeks. Increments of colony formation were also obtained in Tx-D SAA patients, but in the first week of culture only.

IN CONCLUSION

1) a significant impairment of SL formation was seen in BMT recipients, but not in SAA patients; 2) a significant increment of granulocyte-macrophage colony-forming units (CFU-GM) growth can be obtained in patients with marrow failure early after starting long-term culture; 3) the number of CFU-GM grown in these culture conditions from Tx-I SAA patients parallels the number of progenitors from early post-BMT recipients; and 4) progenitor cells from Tx-D SAA patients are not only reduced in numbers, but also exhibit a poor ability to survive in LTBMC.

Response of CFU-GM to increasing doses of rhGM-CSF in patients with aplastic anemia

The aim of this study was to test whether large amounts of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) are capable of promoting the growth of hemopoietic progenitors from patients with marrow failure. For this purpose 0.1, 100, 1000, 10,000 and 20,000 ng/ml of rhGM-CSF were added to 10(5) light-density (adherent cell-depleted) bone marrow cells from 9 normal controls and from 52 patients with aplastic anemia, 25 cases of which were transfusion-dependent (Tx-D) aplastic anemia (AA) and 27 of which were transfusion-independent (Tx-I) aplastic anemia (AA). A dose-dependent increase of granulocyte-macrophage colony-forming units (CFU-GM) was observed in healthy donors, from 81 to 247 colonies at 0.1 and 1000 ng/ml of rhGM-CSF, with a plateau thereafter. Tx-I AA patients showed the best increase of CFU-GM in response to colony-stimulating factor, from 0.1 to 32.7 mean colonies at 0.1 and 20,000 ng/ml of rhGM-CSF, and the increment was greater when compared to controls. The ratio of CFU-GM grown from these patients and controls was 1:810 at 0.1 ng/ml of rhGM-CSF and 1:7.9 at 20,000 ng/ml. Eleven patients were studied at diagnosis; there was no in vitro response to rhGM-CSF (0 and 1.8 mean colonies/10(5) cells at 0.1 and 10,000 ng/ml). Overall, Tx-D AA patients showed minimal increments of CFU-GM growth at very high doses of rhGM-CSF. Two suggestions come from this study: 1) maturation of CFU-GM from recovering AA patients appears to require larger doses of GM-CSF than normal controls, and 2) very high doses of rhGM-CSF have little or no effect on CFU-GM growth in AA patients. This may be relevant for clinical studies designed to improve hemopoiesis in patients with marrow failure.

Use of digoxigenin-labelled probes for detection and host-range studies of tomato yellow leaf curl geminivirus

We studied the host range of tomato yellow leaf curl virus (TYLCV) in some agronomically important tomato species. Transmission tests with the natural vector Bemisia tabaci from tomato to sweet pepper, eggplant, cucumber, melon, zucchini and spinach showed that these species did not develop symptoms and did not support viral replication. These species therefore do not constitutive a reservoir of the virus and can be cultivated as alternatives to tomato in the most affected areas. For host-range studies, we used a quick and sensitive dot-blot assay employing non-radioactive DNA probes. This technique, developed for detecting TYLCV in plant extracts, is easily used for diagnosis. The sensitivity of this non-radioactive test was comparable to that of radiolabelled probes.

In vitro transcription of the double-stranded RNA genome of maize rough dwarf virus (Reoviridae)

An RNA-dependent RNA polymerase associated with particles of maize rough dwarf virus, a Fijivirus, was characterized using two in vitro assays differing in their energy regeneration systems. Optimum reaction rates occurred at pH 8.0 to 8.5 at 20 degrees C. The presence of virus and Mn2+ or Mg2+ was essential for enzyme activity; Mn2+ stimulated more incorporation events than Mg2+, at optimum concentrations of 2 to 4 mM and 4 mM, respectively. Incorporation was not affected by alpha-amanitin, actinomycin D or rifampicin. The products synthesized in vitro were single-stranded RNAs which hybridized specifically with the double-stranded genomic RNAs of five other reoviruses. The in vitro transcripts were also used to detect maize rough dwarf virus RNA in plants and in vector insects.