PubMed Health⌕ Search

Biomedical subjects

L Calvert

Publications and source records attributed to L Calvert.

10 recordsLinked to original sources
PubMed2002

Expression and inheritance of hypersensitive resistance to rice hoja blanca virus mediated by the viral nucleocapsid protein gene in transgenic rice.

Rice hoja blanca virus (RHBV) is a major virus disease of economic importance affecting rice in northern South America, Central America and the Caribbean. This is the first report of transgenic resistance to RHBV and the transformation of an indica rice variety from Latin America. Rice transformed with the RHBV nucleocapsid protein ( N) gene had a significant reduction in disease development. Several reactions were observed that ranged from susceptible to completely resistant plants (immunity). The resistant reactions were characterized by the production of local lesions like a hypersensitive reaction or a recovery phenotype with the emergence of symptom-less new leaves. These transgenic RHBV-resistant rice lines expressed the N gene RNA at low levels that were below the detection limit by Northern blots and only resolved by RT-PCR. The nucleocapsid protein could not be detected in any of the transgenic plants either by Western or ELISA tests. These results suggest that the resistance encoded by the N gene in these plants appears to be mediated by RNA. When challenged with RHBV, the resistant transgenic lines showed a significant increased performance for important agronomic traits including the number of tillers, the number of grains per plant and the yield as compared to the susceptible control. Furthermore, upon inoculation some of the most-resistant transgenic lines showed agronomic traits similar to the uninoculated non-transgenic Cica 8 control. Using both agronomic traits and disease severity as criteria, several of the most-resistant lines were followed through the R(4) generation and demonstrated that the N gene and RHBV resistance was inherited in a stable manner. These transgenic rice lines could become a new genetic resource in developing RHBV-resistant cultivars.

Capsid Proteins↗
PubMed2001

Potato yellow mosaic virus: a synonym of tomato yellow mosaic virus.

Tomato yellow mosaic was first described in 1963, as a disease caused by a geminivirus transmitted by the whitefly Bemisia tabaci in Venezuela. In 1981 and 1985, Tomato yellow mosaic virus (ToYMV) was reported to occasionally infect potato plants growing in the proximity of tomato plantings affected by this virus. Despite these previous reports, a virus isolated from yellow mosaic-affected potato plants in Venezuela, was described in 1986 as a "new geminivirus" called potato yellow mosaic virus (PYMV). In recent years, different geminiviruses related to PYMV have been described from tomato fields in Venezuela and other countries in the Caribbean Basin, including Panama. Comparative nucleotide and amino acid sequence analyses of a 1698 bp fragment amplified from the common region and part of the AV1 and AC1 ORFs of ToYMV from Venezuela, yielded 95.7% sequence identity with the corresponding regions of PYMV. Nucleotide and amino acid sequence identities between ToYMV and PYMV, were 96.3% and 95.1% for AC1, and 95.7% and 100% for AV1, respectively. The identity of the nucleotide sequence for the common region of ToYMV and PYMV was 96.5%. Comparative sequence analyses conducted with ToYMV and other tomato begomoviruses present in the Caribbean region, showed only distant relationships. It is concluded here that PYMV is a synonym of ToYMV.

Geminiviridae↗
PubMed1998

Chemotherapy immediately following autologous stem-cell transplantation in patients with advanced breast cancer.

Most patients relapse after high-dose chemotherapy (HDCT) with autologous stem-cell transplantation (ASCT) for metastatic breast cancer. Further chemotherapy immediately after hematopoietic recovery from ASCT is not given for fear of irreversibly damaging the newly engrafted stem cells. In a pilot chemoprotection trial, autologous CD34+ cells from patients with metastatic breast cancer were exposed to a replication-incompetent retroviral vector carrying MDR-1 cDNA and then reinfused after HDCT. Immediately on recovery, patients received multiple courses of escalating dose paclitaxel. All of the 10 patients tolerated reinfusion of modified cells without any toxicity and had myeloid engraftment within 12 days (range, 11-14). The bone marrow cells of three patients contained vector MDR-1-positive cells only at the time of the first course of posttransplant paclitaxel, indicating that the MDR-1 vector-modified cells had only short-term engrafting potential. A total of 83 courses of paclitaxel were administered starting at a median of 30 (range, 21-32) days from ASCT. The median dose of paclitaxel was 225 mg/m2 and the median interval between paclitaxel cycles of therapy was 21 (range, 20-41) days. Five of the six CR patients were able to receive all of the 12 courses of paclitaxel. Three patients who had achieved less than a complete response to the HDCT (2 patients) and partial response (1 patient) were converted to complete clinical responses during the 12 cycles of paclitaxel. No delayed toxicity or bone marrow failure was noted in these patients with a median follow-up of 2 years from ASCT. This is the first study of chemotherapy immediately after transplantation with autologous CD34+ cells. These data indicate that paclitaxel can be safely administered immediately after ASCT without any delayed toxicities. Paclitaxel given immediately after ASCT can further improve the response to pretransplant chemotherapy in patients with advanced breast cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Evidence that DNA-A of a geminivirus associated with severe cassava mosaic disease in Uganda has arisen by interspecific recombination.

Geminivirus isolates associated with the epidemic of severe cassava mosaic disease in Uganda were studied and compared with virus isolates from the part of Uganda outside the epidemic area, and with African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV). Isolates of a novel type [the Uganda variant (UgV)] were detected in severely affected plants from the epidemic area, whereas those from plants outside the epidemic area were typical of ACMV. The complete nucleotide sequences of DNA-A of UgV (2799 nt) and of a Tanzanian isolate of EACMV (2801 nt) were determined and are extremely similar, except for the coat protein (CP) gene. The CP gene of UgV has three distinct regions: the 5' 219 nt are 99% identical to EACMV (only 79% to ACMV); the following 459 nt are 99% identical to ACMV (75% to EACMV); and the 3' 93 nt are 98% identical to EACMV (76% to ACMV). UgV DNA-A therefore is considered to have arisen by interspecific recombination of EACMV and ACMV. Despite the hybrid nature of their CP, UgV isolates were indistinguishable from ACMV in tests with 20 monoclonal antibodies (MAbs), including seven which reacted with ACMV but not EACMV. The discontinuous epitopes detected by these seven MAbs must involve amino acids which lie in the central part of the CP (residues 74-226) and which differ in ACMV and EACMV. UgV isolates were detected in severely mosaic-affected plants from all 11 widely separated locations sampled. The probable role of recombination in geminivirus evolution in the short to medium term is discussed.

Base Sequence↗
PubMed1995

Percentage of Philadelphia chromosome (Ph)-negative and Ph-positive cells found after autologous transplantation for chronic myelogenous leukemia depends on percentage of diploid cells induced by conventional-dose chemotherapy before collection of autologous cells.

We collected peripheral blood mononuclear cells and bone marrow cells soon after recovery from conventional-dose chemotherapy-induced myelosuppression and transplanted these cells into advanced chronic myelogenous leukemia (CML) patients after treating these patients with 120 mg/kg cyclophosphamide, 750 mg/m2 VP-16, and 1,020 cGy of total body irradiation (TBI). Of the 10 late chronic-phase patients and the eight accelerated-phase CML patients evaluable posttransplant, 90% and 87%, respectively, remain alive posttransplant, whereas none of the three blast crisis CML patients given this therapy remain alive posttransplant. We measured the percentage of Philadelphia chromosome (Ph)-negative cells in the autologous cells collected after conventional-dose chemotherapy-induced myelosuppression before autologous transplant and in the marrow of these same CML patients after autologous transplantation of these cells into recipients treated with the cyclophosphamide, VP-16, and TBI. A direct correlation (correlation coefficient = 0.91) was observed between the level of Ph+ cells in the transplanted cells and the percentage of Ph+ marrow cells after transplant in 21 patients so transplanted. The data show that the chance of generating cytogenetic remissions post-transplant depends on the percentage of diploid cells in the preparations of autologous cells used for transplant and the stage of disease of the patients at the time of collection of the autologous cells.

Adult↗
PubMed1995

Collection of peripheral-blood diploid cells from chronic myelogenous leukemia patients early in the recovery phase from myelosuppression induced by intensive-dose chemotherapy.

PURPOSE: To evaluate whether intensive chemotherapy followed by peripheral stem-cell (PSC) collections during early hematopoietic recovery results in a higher percentage of diploid cell collections in patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML). PATIENTS AND METHODS: Fifty-five adults with Ph-positive CML received intensive chemotherapy with daunorubicin and high-dose cytarabine (ara-C) (DAUNO-HDAC; 26 patients) or fludarabine, high-dose ara-C, and mitoxantrone (FAM; 29 patients). Collections of the peripheral mononuclear cells were initiated when the WBC count was > or = 0.8 x 10(3)/microL. Simultaneous peripheral and marrow samples were subjected to cytogenetic studies. RESULTS: Thirty-eight of 55 patients (69%) were able to undergo the PSC collections. The rate of collection was higher in chronic phase (26 of 30 patients; 87%) than in accelerated (11 of 17; 65%) and blastic phases (1 of 8; 12%). Among the 30 patients in chronic phase, cytogenetic analyses of PSC showed cytogenetic responses (Ph-positive < 95%) in 60%, which were major (Ph < 35%) in 43% and complete (Ph = 0%) in 27%. Seven of 19 patients with simultaneous studies (37%; 23% of total) had a significantly lower percentage of Ph-positive cells in the peripheral collection compared with the marrow collection; one had the reverse phenomenon (5%; 3% of total). Cytogenetic responses were modest in both peripheral and marrow collections in CML accelerated and blastic phases. Myelosuppression-associated complications were frequent, resulting in febrile episodes in 76% of patients. CONCLUSION: PSC collection during early hematopoietic recovery from intensive chemotherapy allowed the collection of diploid-rich stem cells, mostly in chronic-phase CML. The approach could be used for in vivo purging before autologous stem-cell transplantation (ASCT).

Adolescent↗
PubMed1992

Clinical implications of decreased retinoblastoma protein expression in acute myelogenous leukemia.

The retinoblastoma (RB) protein levels in blast-enriched mononuclear fractions from the peripheral blood of 33 newly diagnosed patients with acute myelogenous leukemia were studied. Ten patients who had previously been treated were also analyzed, nine of whom had achieved prior complete remission. Low RB protein expression was found in 13 of 43 (30%) of the acute myelogenous leukemia patients as determined by Western blotting and immunochemical analysis. Of particular interest among the 20 newly diagnosed patients treated with the same therapeutic regimen, the median survival was 39 days for those with low RB protein expression compared to 333 days for those with high levels of RB protein expression in their leukemic cells (P less than or equal to 0.02). This preliminary study suggests that decreases of RB protein expression in peripheral blood of myeloid leukemic cells occur frequently and may be associated with shortened survival of acute myelogenous leukemia patients.

Blotting, Western↗
PubMed1973

Evidence that the ciliary inhibitor of cystic fibrosis is not an antibody.

An inhibitor of ciliary activity is present in the serum of cystic fibrosis (CF) patients and heterozygotes. Fractionation of CF serum has indicated that the inhibitor is associated with the serum IgG fraction. This study compared the activity of the CF inhibitor to that of rabbit antibody preparations directed against oyster cilia. The aim of this investigation was to determine whether the ciliary inhibitory mechanism in cystic fibrosis is related to a typical immunological reaction. Results from experiments utilizing fluorescent antibody techniques demonstrated that an antiserum directed against oyster ciliated epithelium binds immunologically with both human bronchial and oyster epithelial tissue. Results from experiments utilizing immunofluorescent tracing, passive hemagglutination, double immunodiffusion, and papain digestion, however, indicated that the interaction between the oyster cilia and the CF serum inhibitor was not a typical antigen-antibody reaction.

Animals↗