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Biomedical subjects

R A Phillips

Publications and source records attributed to R A Phillips.

At least 181 records · Page 10Linked to original sources
PubMed1983

Characterization of early B lymphocyte precursors present in long-term bone marrow cultures.

Lymphoid precursor cells are present in long-term bone marrow cultures (LTBMC), but their differentiation into mature lymphocytes is blocked. A quantitative assay for B cell precursors in LTBMC, which gives a linear relationship between the number of grafted LTBMC cells and the frequency of B cell colony forming units (CFU-B) in the spleen and bone marrow of immunodeficient CBA/N mice 19 days after reconstitution, is described. Characterization of the B cell precursor indicates that this assay is detecting a very early precursor and not a B lymphocyte or a late pre-B cell. This conclusion is based on the observations that a) pre-B cells transformable by Abelson murine leukemia virus are not present in LTBMC by 3 days postrecharge and CFU-B are absent by 6 days postrecharge; b) late B cell progenitors capable of rapid repopulation of irradiated CBA/N mice are not present in LTBMC, since a lag in the kinetics of B cell reconstitution in animals grafted with LTBMC cells is observed compared with fresh bone marrow cells; c) the B cell precursors in LTBMC have high proliferative potential, since they can stably repopulate recipient mice for at least 8 wk postreconstitution and through two serial passages in irradiated CBA/N recipients; and d) the B cell precursors are large, rapidly sedimenting cells as determined by velocity sedimentation. The serial transplantation experiment further shows that a split is often observed between lymphoid and myeloid reconstituting ability of LTBMC cells. The LTBMC B cell precursor may be a pluripotent stem cell or a lymphoid stem cell, although its differentiative potential remains to be determined.

Abelson murine leukemia virus↗
PubMed1982

Adenovirus-12 genes undetectable in human retinoblastoma.

Retinoblastoma is a rare eye tumor found predominantly in young children. Intra-ocular injection of adenovirus-12 (Ad-12) into newborn recipients induces in rats and in baboons tumors morphologically similar to human retinoblastoma tumors. In addition, Ad-12 DNA can transform human embryonic retinal cells and the transformed cells form retinoblastoma-like tumors in nude mice. These observations have led to the suggestion that Ad-12 may also be involved in the induction of human retinoblastoma tumors. To test this possibility, DNA and RNA were isolated from six human tumors. Analysis of RNA and DNA by blotting with labelled Ad-12 failed to reveal viral sequences in human retinoblastoma.

Adenoviruses, Human↗
PubMed1982

Fibroblasts from retinoblastoma patients: enhanced growth in fetal calf serum and a normal response to ionizing radiation.

Retinoblastoma is a rare malignant eye tumor found almost exclusively in young children. In 30% of cases, the tumor is bilateral and is inherited as an autosomal dominant trait. In such patients, all of the cells in the body must carry the mutation predisposing to retinoblastoma. To search for the expression of the gene in cells outside the retina, we have studied several in vitro properties of skin fibroblasts from patients with bilateral retinoblastoma. Measurement in low concentrations of fetal calf serum of the initial growth rate and the plating efficiency show that fibroblasts from retinoblastoma donors grow significantly better than those from normal donors. However, we were unable to confirm the results of other investigators that fibroblasts from donors with bilateral retinoblastoma are unusually sensitive to ionizing radiation. In family studies, skin fibroblasts from normal siblings had the same radiation sensitivity as fibroblasts from siblings with retinoblastoma.

Cell Division↗
PubMed1982

Multiple karyotypic changes in retinoblastoma tumor cells: presence of normal chromosome No. 13 in most tumors.

There are conflicting reports on the frequency in retinoblastoma tumor cells of aberrations involving chromosome No. 13. To quantitate the frequency of various chromosome aberrations, we analyzed the karyotypes from the retinoblastoma tumors; all tumors contained chromosome abnormalities. Chromosome No. 13 was altered in only two tumors, but the aberrations in these two cases affected different portions of the chromosome. We have concluded that chromosome aberrations affecting chromosome No. 13 are relatively infrequent in retinoblastoma tumors. Chromosome No.1 was involved in rearrangements in eight tumors; in six tumors the rearrangements lead to trisomy of 1q25-1q32. Seven tumors had aberrations resulting in trisomy of the long arm of chromosome No. 17; the most common aberration was an i(17q) chromosome. Every tumor showed trisomy of the long arm of either chromosome No. 1 or 17. These changes in chromosomes No. 1 and 17 have been observed by others in many different tumors and are not unique to retinoblastoma. In summary, chromosome abnormalities were present in all retinoblastoma tumors studied, but no aberration common to all tumors was found.

Animals↗
PubMed1982

Significance of retinoma and phthisis bulbi for retinoblastoma.

Genetic counseling of retinoblastoma (RB) patients and their families is difficult and inaccurate. The data in this paper show that two ocular lesions, retinoma and phthisis bulbi, are associated with RB and can be useful in diagnosis and counseling. Phthisis bulbi is the end result of many conditions and can only be linked to RB if other evidence is present. Retinomas, on the other hand, have three distinctive clinical characteristics (irregular translucent retinal mass, calcification, and pigment epithelial disturbance) and quite accurately predict the presence of the RB gene. Recognition of the significance of retinoma and phthisis bulbi with respect to the RB gene is critical in genetic counseling. Of 34 individuals studied, 32 with retinoma and five with phthisis bulbi, two thirds had a family history of RB or RB in the other eye, and 23/37 of their offspring developed RB. The clinical course of RB in the six children known to be at risk on the basis of detection of the gene in the parent was significantly better than in 17 children that were symptomatic at the time of diagnosis.

Adult↗
PubMed1982

Retinoma: spontaneous regression of retinoblastoma or benign manifestation of the mutation?

Non-progressive retinal lesions, observed in patients known to carry the gene for retinoblastoma, have in the past been called "spontaneous regression" of retinoblastoma. This term suggests shrinkage of a malignant growth, perhaps in response to some host defence mechanism. On the basis of observations on 30 patients, we propose that the term "retinoma" would be less presumptive and more suitable. Retinoma is clinically defined as a translucent, grey, elevated mass extending into the vitreous from the retina, frequently associated with calcified foci and pigment-epithelium hyperplasia. The diagnosis of retinoma strongly suggests the presence of the retinoblastoma gene, necessitating genetic counselling and frequent observation of the retinas in the individual and his offspring. We suggest that the same mutations can cause either retinoma or retinoblastoma: benign hyperplastic nodules or retinoma when the mutations occur in relatively mature retinoblasts; and malignant retinoblastoma when the same mutations arise in immature retinoblasts.

Adolescent↗
PubMed1982

Maturational state of lymphoid cells in long-term bone marrow cultures.

B lymphocytes are not produced in long-term bone marrow cultures (LTBMC) and controversy exists regarding T cell differentiation in the cultures. By analyzing the kinetics of B cell reconstitution in lethally irradiated mice by cells from fresh bone marrow or from LTBMC, we have determined that B cell differentiation is blocked at an early stage in the cultures. Colony-forming B cells (CFU-B) are generated more rapidly and to higher levels in recipients of fresh bone marrow cells than in animals grafted with cells from LTBMC. The data further indicate that the adherent fraction cells from LTBMC are an enriched source of B cell precursors as compared to non-adherent cells and that B cell reconstitutive potential and levels of spleen colony-forming stem cells (CFU-S) do not correlate with one another. Under appropriate culture conditions, T lymphocytes are detectable in LTBMC. These Thy-1-positive cells proliferate in the cultures and can generate cytotoxic responses. These effectors originate from Thy-1-positive cells present in the initial bone marrow inoculum used to establish the cultures and have not differentiated from mature Thy-1-negative progenitors in vitro.

Animals↗
PubMed1982

Reproducible growth in tissue culture of retinoblastoma tumor specimens.

Retinoblastoma is a unique embryonic tumor which frequently arises because of an autosomal dominantly inherited mutation. Study of the genetic changes associated with retinoblastomas requires techniques that allow proliferation of fresh tumor specimens in tissue culture. However, until the present study, there were no reported methods for routinely obtaining in vitro growth of fresh retinoblastoma tumor cells. When placed on selected fibroblast feeder layers, 65% of fresh retinoblastoma specimens grew; but in the absence of fibroblasts, the same specimens died. Individual fibroblast strains from normal donors, retinoblastoma patients, and mice were effective feeder layers. A fibroblast strain that provided good feeder function for one tumor generally supported growth of other tumors also. Direct contact was required between the tumor cells and the fibroblast; conditioned media alone did not support tumor growth and immobilization of tumor cells in semisolid media above fibroblasts failed to give colony growth. Cultured tumor cells injected into the eyes of athymic nude mice formed tumors histologically characteristic of retinoblastomas.

Cell Division↗
PubMed1981

Stimulation of human NK cell activity by cultured cells. II Ingestion of aspirin by blood donors suppresses induced NK activity.

Incubation of mononuclear cells with a melanoma tumour cell. M4, induces a rapid increase in NK cell activity in both normal and tumour patient cells. A marked individual variation among the patient population can be attributed to the prior ingestion of aspirin. Single therapeutic doses of aspirin (two tablets, 660 mg) taken 12 hr prior to donation of the blood sample cause an 80-100% reduction in the NK cell activity induced by M4. Since many patients coming to cancer clinics take aspirin regularly, it is essential that they be questioned about their recent usage of this drug if their cells are to be used in assays for NK activity.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1980

Enhanced lymphoid and decreased myeloid reconstituting ability of stem cells from long-term cultures of mouse bone marrow.

Mature, functional lymphocytes rapidly disappear from long-term cultures of mouse bone marrow cells and never reappear. One reason for the loss of B lymphocytes is that the optimal culture conditions for maintenance of myeloid stem cells are suboptimal for lymphocyte survival. However, despite the absence of functional lymphocytes, stem cells from such cultures retain the ability to reconstitute irradiated mice with mitogen-responsive B and T lymphocytes. In fact, in vitro grown stem cells repopulate the lymphoid system better than the myeloid system; the defective myeloid potential does not result from the absence in the cultures of Thy--1 bearing regulatory cells (TSRC). Although the cultures lack mature lymphocytes, they contain putative T cell precursors detectable with an in vitro colony-forming assay (CFU-T). In vitro maintenance of CFU-T requires an appropriate adherent monolayer. Monolyaters from congenitally anemic mice of genotype Sl/Sld fail to support either myeloid precursors or CFU-T.

Animals↗
PubMed1980

Differentiation of Thy 1-bearing cells from progenitors in long-term bone marrow cultures.

Lone-term marrow cultures, established according to the technique described by Dexter, contain a colony-forming cell (CFU-T) that produces Thy 1-positive progeny after stimulation with PHA-induced conditioned medium from human leukocytes. When 10(-7) M hydrocortisone is added to the medium for the long-term cultures CFU-T can be maintained in vitro for at least 16 weeks. Cells from individual colonies lack precursors for cytotoxic lymphocytes but can provide nonspecific help required for the generation of cytotoxic lymphocytes.

Animals↗
PubMed1980

The use of hydroxyurea to study the proliferative state of T-cell precursors (CFUT) in murine bone marrow.

The cycle specific drug, hydroxyurea (HU), has previously been used to study the proliferative kinetics of various hemopoietic precursor cells such as granulocyte-macrophage precursors (CFUc) and multipotential stem cells (CFUs). We have investigated the kinetics of another hemopoietic precursor, a T-cell colony (CFUT). When mice are exposed to two doses of HU, separated by 7 h, CFUT are reduced to approximately 30% of the control value. Surviving cells in the bone marrow quickly replenish the population and return it to normal values 2 days after HU treatment. When fresh bone marrow cells or bone marrow cells harvested from mice exposed 24 h earlier to HU are treated in vitro with HU, CFUT activity is reduced by approximately 70%. These data indicate that CFUT is a rapidly proliferating population with a large proportion of the cells always in cell cycle.

Animals↗
PubMed1980

Potentials for lymphoid differentiation by cells from long term cultures of bone marrow.

Dexter has described a culture system in which pluripotent stem cells (CFUs) are maintained for several months on an adherent layer derived from bone marrow. The population of cells floating in the supernatant medium contains stem cells and other cells at later stages of myeloid differentiation. Mature lymphocytes have not been observed in these cultures. Since the culture conditions may select for stem cells restricted to myeloid differentiation, we have studied the differentiative potential of cultured stem cells. Cultures were established using various combinatins of CBA bone marrow and CBA/HT6T6 bone marrow to distinguish between adherent layer derived cells and "recharge" derived cells. After various intervals in culture, cells were injected into irradiated recipients of either CBA or CBA/HT6T6 genotype. Three to four months after reconstitution, mitotic spreads were prepared from proliferating lymphoid and myeloid cells. The results showed that cells capable of giving rist to both B and T lymphoid progeny were maintained in culture for six weeks. The origin of the nonadherent CFUs in these cultures were also examined. They were derived from both the adherent and the "recharge" cell populations.

Animals↗