PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Serial Passage”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMedDate not supplied

Attenuation of Eimeria necatrix and E. tenella of U.S. origin by serial embryo passage.

Two lines of Eimeria tenella (PS and FS65) and one line of E. necatrix (FS144) of U.S. origin were passaged in chicken embryos. The embryo-passaged line of E. tenella PS was significantly less pathogenic than the parent line when tested in chickens after 33 embryo passages. After 29 embryo passages, E. tenella FS65 was just as pathogenic to chickens as the parent line. A comparison of the immunogenicity of the embryo-adapted lines and the parent lines in chickens showed that embryo-passaged E. tenella PS and E. tenella FS65 were as immunogenic as parent lines. The embryo-passaged line of E. necatrix FS144 was significantly less pathogenic when tested in chickens after 30 embryo passages. Although there was also some loss of immunogenicity in the embryo-passaged line of E. necatrix, immunity to this parasite could be achieved by increasing the dose of oocysts.

Animals↗
PubMedDate not supplied

Avian paramyxovirus type 1 from pigeons: isolate characterization and pathogenicity after chicken or embryo passage of selected isolates.

Nine pigeon paramyxovirus type 1 isolates from the United States and Canada were characterized and three of the isolates were pathotyped before and after passage in chickens and serial passage in chicken embryos. One isolate previously passaged in Madin Darby bovine kidney cells was also pathotyped after chicken and embryo passage. Hemagglutination (HA) titers of all isolates were low when tested by microtiter procedures and all were negative by rapid-plate HA. The HA titers were increased by a factor of 8 to 32 by Tween-ether treatment, and treated antigen had the same reactivity as untreated antigen in hemagglutination-inhibition (HI) tests. All isolates had a slow elution rate and an HA thermostability equal to or greater than 60 minutes. Mean death times in embryos were 99 hours or greater, except for one isolate with a mean death time of 81 hours, and intracerebral pathogenicity indices of all isolates were greater than 1. Antigenic differences among the pigeon isolates were identified by three different binding patterns in HI tests against a battery of five Newcastle disease virus (NDV) monoclonal antibodies. Pathogenicity enhancement by bird, embryo, or cell passage was limited to an intravenous pathogenicity index increase for one of three viruses passaged in embryonated eggs. Cloacal samples collected during chicken passage contained higher virus titers than did oral samples. The pigeon isolates reported here, like those of earlier reports, have properties that prevent characterization within a single NDV pathotype. Finally, there was no evidence that any of these isolates was highly virulent for chickens.

Animals↗
PubMed1989

Osteosarcoma and interferon. Studies of human xenografts in the nude mouse.

This work assessed the transplantability of human osteosarcomas to immunodeficient nude mice. Osteosarcomas serially transplanted in nude mice were characterized by growth rate, histologic features, and nuclear DNA content. The osteosarcoma xenografts were used to investigate the antitumor effects of interferon (IFN). Tumor tissue from 25 primary osteosarcomas was transplanted into nude mice. All tumors were histologically of high grade (III-IV). Flow DNA cytometry disclosed that all, except 1, had a nondiploid DNA content. 14 of the 25 osteosarcomas grew in serial passage in nude mice, i.e., the take rate was 0.6. The transplantable osteosarcoma group was characterized by a predominance of Grade IV lesions, and a high proportion of proliferating cells, compared to the nontransplantable. The 14 osteosarcoma xenografts, established in nude mice, were heterogeneous with respect to growth rate, histologic subtype, DNA content, and proliferative activity. However, the osteosarcomas retained the basic characteristics of their respective original tumor; the xenografts exhibited the same histologic appearance and DNA content in the first 2 passages in nude mice. During serial transplantation of the 14 osteosarcomas, the histologic features remained unaltered from passage to passage during the observation period of up to 3 years. The aneuploid DNA content was also unchanged over time in most tumors. However, in 4 osteosarcomas with 2 aneuploid cell populations, the cell population with the higher DNA content became predominant, while the other gradually disappeared. Hence, the changes in DNA content involved polyploidization, followed by selection of the cell population with higher DNA content. At the same time growth rate increased, but histologic features were unchanged. This study of osteosarcoma, serially transplanted in nude mice, shows that growth rate, histologic appearance, and DNA content are relatively stable tumor features. The observed changes in DNA content illustrate the development of aneuploidy in malignant tumors. The antitumor effects of human nIFN-alpha were assessed in the 14 osteosarcoma xenografts. In dose-response experiments, based on 2 different tumors, 2 x 10(5) IU/day of nIFN-alpha was found to arrest tumor growth. This dose was chosen as the standard dose in subsequent experiments. Among the 14 osteosarcomas, tumor regression or growth arrest was seen in 5, whereas 8 were only partially growth inhibited with the standard dose. The remaining osteosarcoma was growth inhibited with higher nIFN-alpha doses. Hence, all 14 analyzed osteosarcomas were sensitive to the antitumor effect of nIFN-alpha.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Improved sensitivity of a modified polymerase chain reaction amplified DNA probe in comparison with serial tissue culture passage for detection of Chlamydia trachomatis in conjunctival specimens from nepal.

A sensitive means for detecting ocular chlamydial infections is needed to accurately define the epidemiology of trachoma. Tissue culture is considered the "gold standard," yet it is less than 50% sensitive for ocular specimens. The purpose of this study was to improve the detection rate of culture by serial passage and thereby provide a more reliable basis for comparing polymerase chain reaction (PCR) amplified and 32P DNA probes and direct fluorescent antibody (DFA) tests with culture. Ocular exams on 1043 individuals were scored for trachoma; 252 (24%) had moderate/severe intensity. A total of 1214 conjunctival samples were collected and passaged twice. Of 1053 samples, 276 negative at second passage were passaged an additional two times. The vast majority (93%) of all culture-positive samples were recovered by first passage. Only 80 of 252 cases (32%) with moderate/severe intensity were diagnosed by culture. The sensitivity of the 32P and PCR probes were 87% and 90%, respectively. For DFA versus culture, the sensitivity rate was 48%. Our results indicate that true rates of infection can not be accurately determined by culture even with serial passage. The sensitivity of the probes and DFA tests may, therefore, be higher. The PCR probe holds promise as an epidemiologic tool for studying chlamydial ocular infections.

Chlamydia trachomatis↗
PubMed2002

Subclinical scrapie infection in a resistant species: persistence, replication, and adaptation of infectivity during four passages.

Cross-species infection with transmissible spongiform encephalopathy agents may lead to subclinical infection and to adaptation of the infection to new species. This is of particular concern for the millions of people possibly exposed to bovine spongiform encephalopathy (BSE) by consumption of BSE-infected beef. Subclinical infection was studied by making 4 serial passages of hamster scrapie agent (263K) in mice. At each step, infectivity was followed by inoculation of hamsters and mice. Subclinical infection was demonstrated either by detection of abnormal protease-resistant prion protein (PrP-res) or in the absence of PrP-res by detection of infectivity. Replication and adaptation of hamster infectivity in mice was shown in year 2 after initial mouse passage. In third and fourth passages, dual-tropic, mouse-tropic, and hamster-tropic infectivity was found in different animals. In some cases infectivity similar to the original 263K hamster scrapie strain was found after 2 or 3 serial mouse passages totaling 1200-1550 days.

Adaptation, Physiological↗
PubMed2005

Recurrent mutations associated with isolation and passage of SARS coronavirus in cells from non-human primates.

Four clinical isolates of SARS coronavirus were serially passaged in two primate cell lines (FRhK4 and Vero E6). Viral genetic sequences encoding for structural proteins and open reading frames 6--8 were determined in the original clinical specimen, the initial virus isolate (passage 0) and at passages 5, 10, and 15. After 15 passages, a total of 15 different mutations were identified and 12 of them were non-synonymous mutations. Seven of these mutations were recurrent mutation and all located at the spike, membrane, and Orf 8a protein encoding sequences. Mutations in the membrane protein and a deletion in ORF 6--8 were already observed in passage 0, suggesting these amino acid substitutions are important in the adaptation of the virus isolate in primate cell culture. A mutation in the spike gene (residue 24079) appeared to be unique to adaptation in FRhK4 cells. It is important to be aware of cell culture associated mutations when interpreting data on molecular evolution of SARS coronavirus.

Adaptation, Biological↗