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 37 records · Page 2Linked to original sources

PubMed1984

Stability of the pseudorabies virus genome after in vivo serial passage.

Restriction endonuclease patterns of pseudorabies virus (PRV) DNA were examined after each of 11 serial passages of the virus through pigs. Minor variations in the electrophoretic mobility of certain restriction enzyme fragments were observed by the sixth passage. This variability was similar to some of the minor variability observed in field isolates. The variable fragments were mapped to three locations on the PRV genome: the junction between the short unique sequences and the repeat sequences, the terminus of the long unique region, and an internal area of the long unique region.

Animals↗

PubMed1985

Tumor progression in serial passages of the Dunning R3327-G rat prostatic adenocarcinoma: growth rate response to endocrine manipulation.

Serial passages of the poorly differentiated, androgen-sensitive R3327-G prostatic adenocarcinoma were used to study the progressive changes that occur in tumor growth rate and androgen sensitivity. Different in vivo transplant generations (21st to 28th) were compared. The tumor doubling and animal survival times resulting from the implantation of the 21st to 22nd generation (21-22G) tumor cells in intact male rats were significantly greater than those resulting from the implantation of 23-28G tumor cells. The most dramatic difference between early (21-23G) and late (26-28G) tumor generations, however, was in androgen sensitivity. The 26-28G tumors displayed androgen sensitivity only when implanted into animals castrated 2 to 7 days previously. Tumors grown in the pretreated castrates grew at a significantly slower rate than those in intact rats and the pretreated castrates had longer survival times than the intact rats. When 26-28G tumors were allowed to grow in intact rats to approximately 1 cu cm and then the rats were castrated, no significant difference in the growth rate between these tumors and tumors grown in intact rats was observed. In contrast, the androgen sensitivity of 21-23G tumors could be demonstrated, regardless of whether treatment was started before or after implantation. The fact that androgen sensitivity was still evident under certain conditions in late-generation R3327-G tumors demonstrates that the basic mechanism involving androgen response was still present, although functioning at a much reduced level.

Adenocarcinoma↗

PubMed1985

The alterations in pathogenicity and immunogenicity of a Kenya sheep and goat pox virus on serial passage in bovine foetal muscle cell cultures.

A Kenyan sheep and goat pox virus was attenuated by serial passage in bovine foetal muscle cell cultures. The pathogenicity of the strain was lost between the 15th and 20th passages. Serum-neutralizing antibody developed after inoculation with passages tested up to the 50th. These passages appeared to protect animals against laboratory challenge by intra-dermal titration. The 18th passage was successfully and extensively used to control the disease under field conditions.

Animal Diseases↗

PubMed1986

Growth and ploidy of human osteosarcoma xenografts in serial passage in nude mice.

Six human osteosarcoma tumors have been transplanted to and maintained as xenografts in serial passage in nude mice. The xenografts, characterized by growth rate, histologic appearance, and DNA flow cytometric data, are now in the 6-17 passages in mice. Histologic appearances and growth rates of the xenografts were unchanged through all passages except for one xenograft in which the growth rate doubled in passage 3. All six tumors had hyperploid DNA contents. The ploidy levels were unchanged, compared to their original tumors, in all passages of five xenografts. One xenograft, concomitantly with the increase in growth rate, also doubled the ploidy from 2.8 to 5.6C. There was a good agreement between the proportion of S-phase cells and mitotic indices of the six xenografts. The growth rate, depending also on cell loss, was less related to the proliferative activity of the xenografts. It was concluded that osteosarcomas have a stable aneuploid DNA content in nude mice, but polyploidization can occur after a number of passages.

Animals↗

PubMed1992

Identification of murine thymocyte populations capable of extensive proliferation in serially passaged thymic organ cultures.

Using the approach of titrating precursor cells into mouse thymus organ cultures and serial passage, we have sought to compare the proliferative capacities of cells derived from adult and embryonic thymus and related haemopoietic tissues. We find that cells derived from the liver and thymus of day 14 embryos are capable of extensive proliferation in such cultures (surviving for at least 12 weeks) whereas cells derived from adult sources (blood and thymus) display a much more restricted lifespan and potential for division. Analysis of sequentially passaged thymic lobes shows that cells lacking CD4 and CD8 (CD4- and CD8-) and a subset of single CD8 positives are selectively expanded in these cultures. A preliminary study of the CD4-CD8- populations in these lobes suggest that these include cells expressing surface CD3 (in association with either TCR alpha beta or TCR gamma delta) and a subset of CD4-CD8-CD3-. These findings suggest that sequential passage of thymocytes in organ culture may be a useful alternative strategy for characterising cells with high proliferative potential, resident in the thymus and also for probing their lineage relationships.

Animals↗

PubMed1978

The DNA of serially passaged herpes simplex virus: organization, origin, and homology to viral RNA.

High-density DNA prepared from serially passaged herpes simplex virus contains three major classes of modified viral DNA molecules. The altered DNA molecules are composed of multiple repetitions of sequences derived from the right-hand side of the S region of the parental plaque-purified viral DNA. The repeat units contained in the three types of high-density DNA share most of their DNA sequences but differ with respect to a small region derived from the unique sequences of the S component of HSV-1 DNA. Hybridization of the defective DNA to HSV-infected cell RNA shows that the high-density DNA contains sequences complementary to both early and late viral transcripts.

Base Sequence↗

PubMed1978

Growth characteristics of human colorectal tumours during serial passage in immune-deprived mice.

The growth characteristics of 6 human colorectal tumours have been examined during serial passage in both male and female immune-deprived mice. Exponential growth is a characteristic feature, especially on very early passages. Growth rates in 5 out of the 6 tumour lines increase during the first few transplant generations. This is accompanied by a shorter exponential growth phase and an increased slope of the growth curves. Lag phases and growth rates for individual tumours are variable within a passage. Growth rates for tumours maintained within the same host are similar, and are at least partially influenced by the host. In one tumour line examined in detail, the increased growth rate is attributable to a decreased cell-loss factor, and the difference in growth rate between human colorectal tumours and their corresponding xenografts may therefore largely be due to a difference in the contribution of this factor.

Animals↗

PubMed1992

Modification of foot-and-mouth disease virus O1 Caseros after serial passages in the presence of antiviral polyclonal sera.

Foot-and-mouth disease virus (FMDV) shows a remarkable antigenic variability and, like other RNA viruses, presents a high rate of mutation. It has been proposed that selection exerted by antibodies of the host could play a major role in the rapid evolution of FMDV. The present work reports the selection of FMDV antibody-resistant (Nr) populations after serial passages of a cloned FMDV O1 Caseros strain on secondary monolayers of bovine kidney cells in the presence of subneutralizing antiviral polyclonal sera (APS). After a limited number of passages, i.e., 29, under selective pressure, the virus population showed the following characteristics: (i) increased resistance to neutralization by APS (Nr), (ii) altered electrophoretic mobility of its structural viral proteins (VP1), and (iii) alterations at the RNA nucleotide sequence that codes for the major antigenic site of VP1. These acquired characteristics were detected at passage 15 and remained unmodified throughout successive passages. These results document a rapid selection and fixation of specific mutations in response to immunological pressure. In addition, the findings that (i) mutations not related to APS selection were not detected and (ii) after 29 passages at a high multiplicity of infection without immunological pressure, the RNA sequence that codes for VP1 remained unmodified clearly demonstrated that FMDV O1 Caseros presents in vitro a remarkable unexpected genetic stability.

Amino Acid Sequence↗

PubMed1991

Selective growth and serial passage of mouse melanocytes from neonatal epidermis in a medium supplemented with bovine pituitary extract.

Suspensions of disaggregated epidermal cells from skins of newborn C57BL/10JHir mice were plated in a growth medium that consisted of Ham's F-10 plus bovine pituitary extract (BPE), insulin, and transferrin. Fetal bovine serum (FBS) was added to the culture medium at a concentration of 4% at the time of plating. On the second day of culture, a small number of melanocytes was randomly distributed among large sheets of keratinocytes. From the third day onward, FBS was excluded from the culture medium to prevent the proliferation of keratinocytes and fibroblasts. The melanocytes began to grow preferentially, and after 12 days pure and enriched populations of melanocytes could be harvested. In the absence of the proliferation of keratinocytes and fibroblasts, melanocytes could be serially passaged in the growth medium supplemented with a conditioned medium (CM) prepared from keratinocyte-enriched cultures, namely, those at the early stages of the primary culture. FBS was added at a concentration of 1% for the first day. These results suggest that both BPE and keratinocyte CM contain growth factors required for proliferation of melanocytes.

Animals↗

PubMed1980

Loss of reiterated DNA sequences during serial passage of human diploid fibroblasts.

A specific family of tandemly repeated DNA sequences was found to diminish in the human genome after serial passage of three strains of diploid fibroblasts. Eco RI restriction fragments of 340 and 680 bp were significantly reduced in quantity at late passage as determined by autoradiography of 14C-DNA and also by ethidium bromide fluorescence. The reduction in these closely related DNA sequences was confirmed by saturation hybridization to excess 14H-RNA transcribed from a homogeneous restriction fragment recleaved from the 340 bp DNA. The maximal fraction of DNA hybridizing to the 3H-RNA probe declined by 33-50% over 21-41 population doublings. Divergence and/or methylation of such sequences could not account for these results since the thermal stability of cRNA:DNA duplexes actually increased by 0.3 degrees C at late passage. Total highly repetitive sequences assayed by reassociation kinetics were also substantially reduced at late passage, implying that depletion may be common to many repeat families in DNA. The denaturation temperature for such rapidly reassociated duplexes again increased slightly at late passage, possibly reflecting the minor decreases in DNA methylation which were detected in two of the cell strains. Karyotype analyses demonstrated that over 95% euploidy was maintained, with no specific chromosome loss and no visible deletions at late passage. The depletion of reiterated sequences during repeated cell division is thus attributed to numerous small DNA deletions, which may arise from unequal recombination coupled with selection or from a nonreciprocal mechanism such as excision.

Cell Division↗

PubMed1971

Virulence and pathogenesis of yellow fever virus serially passaged in cell culture.

Viscerotropic virulence of the Asibi strain of yellow fever virus (YFV) for monkeys has been known to be lost after serial passage in HeLa cell monolayers. This phenomenon was investigated in several other mammalian and insect tissue cell lines. Assay in monkeys of original seed virus and of virus after 7 and 11 passages in a porcine kidney cell line (PK) indicated essentially equal infectivity and mortality. Moreover, monkeys receiving the passaged virus exhibited more rapid onset of disease and death than animals infected with original seed virus. Histological changes in animals inoculated with passaged virus were identical to those in animals receiving the seed virus. Virus from later passages in PK cells was also lethal for approximately 50% of the monkeys; however, evidence for progressive attenuation was seen in these preparations. Similar results were obtained with a mosquito (Aedes aegypti) cell line. In contrast to results obtained in PK and mosquito cells, YFV became essentially avirulent (nonlethal and less infective) for monkeys after only seven passages in HeLa cell cultures.

Aedes↗

PubMed1976

Strain selection during serial passage of Trichoplusia in nuclear polyhedrosis virus.

Two strains of a nuclear polyhedrosis virus (NPV) of Trichoplusia ni were isolated on the basis of plaque morphology. They are designated as MP (having greater than 30 polyhedra per nucleus) and FP (having fewer than 10 polyhedra per nucleus). Serial, undiluted passage of plaque, purified MP nonoccluded. Virus (NOV) in tissue culture led to the production of the FP phenotype detectable at passage 9. With continued serial, undiluted passage, FP became the predominant strain. Comparative growth curves showed that FP NOV are released faster than MP NOV. MP morphology was not observed after 14 serial, undiluted passages of plaque-purified FP. By the plaque neutralization assay, NOV from both strains of virus was neutralized by the homologus and heterologous antisera. The FP phenotype was observed when FP virus was grown in culture at 17, 22, and 27 C. Hence, the FP phenotype was not considered to be the result of temperature-inhibited crystallization of polyhedrin under standard tissue culture conditions. The NOV of both strains killed insects when injected directly into the hemocoele of T. ni larvae. Only MP inclusion bodies were virulent per os. The FP inclusion bodies fed to cabbage looper larvae did not kill, and no infectious agent could be detected in the hemolymph. Electron micrographs of MP polyhedra showed bundles of nucleocapsids of normal length within the polyhedra, whereas FP polyhedra contained heterogeneous, electron-dense material, which could account for their lack of pathogenicity.

Animals↗

PubMed1988

Serial passage of Haemonchus contortus in resistant and susceptible sheep.

A recently isolated field strain of Haemonchus contortus was passaged through resistant (repeatedly reinfected) and susceptible (immunosuppressed) sheep for six and nine generations, respectively. Infectivity of the resulting serially passaged strains was not significantly different when tested in groups of 1-year-old susceptible sheep.

Animals↗

PubMed1987

Biochemical characterization of an aphthovirus type C3 strain Resende attenuated for cattle by serial passages in chicken embryos.

We have compared several aspects of an aphthovirus strain attenuated for cattle (C3R-O/E) with the original strain (C3Res) from which it was derived after serial passages in chicken embryos. Biochemical differences detected by protein analysis in regular polyacrylamide gels (SDS-PAGE) and on electrofocusing gels (NEPHGE) suggest the presence of mutations throughout the genome. Changes were located in coat proteins VP1 and VP3 and in the polymerase precursor P100 (P3/ABCD). No other differences were found at the protein level by means of the techniques used. Polypeptide P100 of the attenuated strain showed a faster electrophoretic mobility in SDS-PAGE with respect to that of the wild-type strain, and the change seems to be located on its amino terminus half. Several functional differences were also found between the two viruses. Both strains grew equally well in BHK cells reaching roughly similar titers in plaque assays. However, the wild-type strain maintained its titer in cells of bovine origin (BK), whereas the titer of C3R-O/E strain decreased approximately one log in this cell system; moreover, plaques elicited by the attenuated strain were much smaller than the ones produced by C3Res. A diminution in the rate of RNA synthesis induced by C3R-O/E in BK cells compared with that of the wild-type strain was also detected; this trait was not observed in BHK cells. A delay in the kinetics of RNA synthesis was also detected in this strain. The virus yield of attenuated strain in BK cells was four times lower than in BHK cells.

Animals↗

PubMedDate not supplied

Serial passage of hepatitis delta virus in chronic hepatitis B virus carrier chimpanzees.

Five consecutive passages of hepatitis delta virus in hepatitis B virus carrier chimpanzees were performed in order to further characterize the infectious and pathogenic nature of this naturally occurring defective virus. Three animals received identical inocula at fourth passage in order to assess individual animal variation as a factor in the course of infection and disease. Acute hepatitis delta virus infection occurred in all hepatitis B virus carrier chimpanzees as demonstrated by coincident intrahepatic hepatitis delta antigen, serum hepatitis delta antigen and serum hepatitis delta virus RNA followed by seroconversion to antibody to hepatitis delta antigen. In all animals, acute hepatitis was temporally associated with hepatitis delta virus infection and was self-limited. The incubation period to hepatitis shortened with passage, whereas biochemical and histologic evidence of liver diseases increased. The marked increase in liver disease with passage was not associated with increasing markers of hepatitis delta virus replication or expression, thus indicating that adaptation to the chimpanzee by serial passage resulted in increased hepatitis delta virus virulence. The duration of hepatitis due to hepatitis delta virus infection in three chimpanzees which received the same inoculum varied from 1 to 8 months. The observations of passage adaptation and individual host variation in this experimental model of hepatitis delta virus disease parallel known pathogenic variations in human hepatitis delta virus infection.

Animals↗

PubMed1987

Measles virus persistence in a hamster brain cell line: cyclical fluctuation of viral expression during serial passages.

Measles virus persistence in a hamster brain cell line was examined for the appearance of viral antigens and for the synthesis of infectious virus, viral RNA, and virus-specific proteins during 19 serial passages. Cyclical fluctuation was detected at all levels of measles virus replication. After reaching the maximal activity at the passages 9 to 11 viral synthesis diminished rapidly, being lowest after 2 to 3 subsequent passages. No release of infectious virus was detected at the passages 14 and 15 and only 20% of the cells contained measles virus antigens when tested by immunofluorescence. After the nonproductive phase, the cells released virus again and the number of antigen-positive cells increased. The alternation in the amount of the measles virus-specific proteins and viral RNA correlated directly with the parameters mentioned above. No apparent defects in the synthesis of individual viral proteins were observed.

Animals↗

PubMed1977

Role of endogenous murine leukemia virus in immunologically triggered lymphoreticular tumors. I. Development and use of oncogenic cellfree preparations serially passaged in vivo.

Cellfree extracts (CFEs) prepared from (BALB/cJ X A/J)F1 (CAF1) and (BALB/cJ X C57BL/6J)F1 (CB6F1) mice in which a graft-versus-host reaction (GVHR) has been induced are known to be oncogenic, but only after a protracted latent period (mean, 16 mo). Serial passage of such CFEs in successive generations of syngeneic mice inoculated at birth led to the development of two separate oncogenic preparations, the CA serioes in CAF, mice and the CB series in CB6F, mice, in which the mean latent period was reduced to 6 and 12 months, respectively. Both oncogenic preparations contained infectious B-tropic murine leukemia virus (MuLV) and particles with the ultrastructural characteristics of MuLV. No other kind of virus particle was seen. When these preparations were injected into infant syngeneic mice, B-tropic MuLV could be detected in the reticular tissues as early as 2 weeks thereafter. The virus persisted in the reticular tissues and was present in the lymphoreticular tumors that subsequently developed. However, if the same preparation was injected into young adult recipients, there may have been transient MuLV replication, but the virus subsequently disappeared from the reticular tissues and no lymphoreticular tumors developed. Previous experiments showed that MuLV was present in CFEs prepared from CAF, animals with the GVHR but absent in those of normal control mice. Since the lymphoreticular tumors arising in mice with the GVHR were the same as those induced by the CA and CB MuLV preparations, it was concluded that tumorigenesis in mice with the GVHR was caused by endogenous B-tropic MuLV activated by the immunologic disturbance.

Animals↗

PubMed1985

Biochemical characterization of an aphthovirus type 0(1) strain campos attenuated for cattle by serial passages in chicken embryos.

The biochemical properties of a virulent and an attenuated strain of foot-and-mouth disease virus (FMDV) Type 0(1) Campos (0(1)C) were compared in order to establish differences that could account for their altered biological functions. The avirulent strain (0(1)C-O/E) was derived from the virulent strain 0(1)C by serial passages in chicken embryos. Analysis of the RNase T1-generated oligonucleotides of the viral RNA through one- and two-dimensional (2D) gel electrophoresis (fingerprints) revealed a few changes in the genome structure of the 0(1)C-O/E strain compared to the wild type strain. In addition there was a significant decrease in the length of the poly(C) rich tract of the 0(1)C-O/E RNA. All virion structural proteins, except VP4, their precursors, and the viral RNA polymerase (p56a) show charge differences. In addition a significant decrease in the apparent molecular weight of polypeptide p100 (primary translational product from the 3' end region of the genome) of the attenuated strain was observed.

Animals↗