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Biomedical subjects

R A Phillips

Publications and source records attributed to R A Phillips.

At least 19 recordsLinked to original sources
PubMed1992

Dynamics and localization of early B-lymphocyte precursor cells (pro-B cells) in the bone marrow of scid mice.

Mice homozygous for the scid (severe combined immunodeficiency) mutation are generally unable to produce B lymphocytes, a condition attributed to defective rearrangement of immunoglobulin genes in precursor B cells. Some early B-lineage cells are present in the bone marrow (BM), however. In scid mice, we defined three subsets of early progenitor B cells lacking mu heavy chains (pro-B cells) based on the expression of terminal deoxynucleotidyl transferase (TdT) and B220 glycoprotein: (a) early pro-B cells (TdT+B220-), (b) intermediate pro-B cells (TdT+B220+), and (c) late pro-B cells (TdT-B220+). Double immunofluorescence labeling of BM cell suspensions has shown normal numbers of early and intermediate pro-B cells, substantially reduced numbers of late pro-B cells, and an absence of pre-B cells and B cells. Early and intermediate pro-B cells accumulated in metaphase in near-normal numbers after intraperitoneal (IP) vincristine administration. B220+ pro-B cells have been localized in BM sections by the binding of intravenously (IV) administered 125I monoclonal antibody (MoAb) 14.8, detected by light and electron microscope radioautography. Many B220+ cells were located peripherally in the bone-lining cell layers associated with stromal reticular cells. More centrally located B220+ cells were frequently associated with macrophages containing prominent cytoplasmic inclusions. Occasional B220+ cells were present in venous sinusoids. These results demonstrate that many pro-B cells in scid mice occupy microenvironments in the BM near the surrounding bone. The pro-B cells maintain normal rates of production during stages of presumptive mu heavy-chain gene rearrangement, apparently unaffected by the absence of a mature B cell pool. Nearly all defective cells then abort at the late pro-B cell stage and are deleted, apparently by macrophages. The findings contribute to models of in vivo differentiation, regulation, localization, and selection of early B-lineage cells in the BM.

Animals↗
PubMed1992

Failure of RB1 to reverse the malignant phenotype of human tumor cell lines.

In addition to retinoblastoma and osteosarcoma, mutation of both alleles of the RB1 gene occurs frequently in several other types of tumors. In order to evaluate the role of RB1 in cancer, the wild type RB1 gene was introduced into the RB1-deleted breast cancer cell line MDA-468-S4 and retinoblastoma cell lines WERI-Rb1 and Y-79. The RB1 complementary DNA was under control of the inducible murine metallothionein promoter in MDA-468-S4 and the thymidine kinase promoter in the retinoblastoma lines. The protein, p110RB1, produced from the exogenously introduced gene appeared normal by immunoprecipitation, Western blot analysis, and nuclear localization and also showed normal cell cycle-dependent phosphorylation and an ability to bind to E1a protein. No changes in growth rate or morphology were observed in either of the reconstituted cell types. Expression of p110RB1 in MDA-468-S4 did not affect anchorage-independent growth when measured by colony formation in soft agar. Although the ability of WERI-Rb1 cells expressing p110RB1 to form colonies in methylcellulose was reduced, the reconstituted retinoblastoma cell lines formed intraocular tumors in immunodeficient mice with the same efficiency as the RB1-negative parent cell lines and the tumors produced by the RB1-reconstituted cells continued to express p110RB1. These experimental results suggest that the malignant phenotype is little affected by the replacement of p110RB1 and that RB1 is a relatively weak tumor suppressor gene.

Animals↗
PubMed1992

Paraphilias: a double-blind crossover comparison of clomipramine versus desipramine.

A relationship has been suggested between clinical presentation of paraphilias and obsessive-compulsive disorder (OCD) with respect to the unwanted repetitive nature and insight into the irrationality of the paraphiliac behavior. This has led to speculation that paraphiliac disorders might belong to an "obsessive compulsive spectrum." To address this issue, and because of the striking selective benefit of serotonin reuptake blocking antidepressants (such as clomipramine) in the treatment of OCD, 15 paraphiliacs entered a double-blind crossover comparison of clomipramine vs. desipramine preceded by a 2-week single-blind placebo period. Four subjects responded to placebo and were dropped from the study. Three others failed to complete the study. Although the study is limited by the small number of patients and the heterogeneity of the paraphilias, the observed benefit from both tricyclics (over the initial placebo) encourages further study. For the 8 subjects completing the protocol, there was no preferential response to the more specific serotonin reuptake inhibitor suggesting a difference in underlying pathophysiology between paraphilia and OCD.

Adult↗
PubMed1992

The retinoblastoma protein and cell cycle regulation.

Although the precise function of the retinoblastoma gene product, p110RB1, remains unknown, recent data suggest that it plays a role in the control of cellular proliferation by regulating transcription of genes required for a cell to enter or stay in a quiescent or G0 state, or for progression through the G1 phase of the cell cycle. However, it is difficult to rationalize the expression of p110RB1 in a wide range of tissues with the fact that mutations in the RB1 gene initiate cancers in a limited number of tissues.

Alleles↗
PubMed1992

How do retinoblastoma tumours form?

The causes of retinoblastoma (RB) can now be described with considerable accuracy, although many details are still unclear. Understanding the genetic changes leading to RB has provided an awareness of general mechanisms of cancer development and progression, previously only suspected. From the basic understanding have come new diagnostic technologies that are now ready to be applied directly to RB patients and their families, and a rational approach, based on this understanding, will help us to develop new therapies that avoid the severe complications of conventional treatment.

Chromosomes, Human, Pair 13↗
PubMed1992

Effects of nifedipine-GITS on left ventricular mass and left ventricular filling.

Sixteen patients with initial diastolic blood pressure greater than or equal to 120 mm Hg were treated for 1 year with extended-release nifedipine [nifedipine-GITS (gastrointestinal therapeutic system)]. Serial changes in left ventricular mass index and associated alterations in left ventricular systolic function, left ventricular filling, plasma renin activity, atrial natriuretic peptide, and catecholamines were evaluated. Blood pressure was significantly reduced from 200 +/- 8/122 +/- 3 mm Hg (mean +/- SEM) to 144 +/- 5/89 +/- 2 mm Hg (p less than 0.0001) at 1 year. Eleven patients (69%) required only nifedipine-GITS for blood pressure control and 5 (31%) required the addition of chlorthalidone. After 6 months, the left ventricular mass index was significantly reduced by 19% from 121 +/- 8 to 96 +/- 7 g/m2 and this reduction was sustained at 1 year. Septal and posterior wall thicknesses were reduced from 13.4 +/- 0.1 to 11.2 +/- 0.04 mm and from 12.8 +/- 0.1 to 10.0 +/- 0.03 mm (p less than 0.001), respectively. Prevalence of left ventricular hypertrophy decreased from 63 to 25%. Left ventricular fractional shortening increased from 34 to 42% (p less than 0.05) and the relationship between fractional shortening and end-systolic stress did not change. Over the year of sustained blood pressure reduction, the peak velocity of early filling increased from 58 to 63 cm/s (p = 0.07), the peak velocity of late filling did not change, and the ratio of late to early peak velocity of left ventricular filling significantly decreased (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1992

Transcriptional repression of the E2-containing promoters EIIaE, c-myc, and RB1 by the product of the RB1 gene.

The protein product of the retinoblastoma susceptibility gene, p110RB1, is a nuclear phosphoprotein [W.H. Lee, J.Y. Shew, F.D. Hong, T.W. Sery, L.A. Donoso, L.J. Young, R. Bookstein, and E.Y. Lee, Nature (London) 329:642-645, 1987] with properties of a cell cycle regulator (K. Buchkovich, L.A. Duffy, and E. Harlow, Cell 58:1097-1105, 1989; P.L. Chen, P. Scully, J.Y. Shew, J.Y. Wang, and W.H. Lee, Cell 58:1193-1198, 1989; J.A. DeCaprio, J.W. Ludlow, D. Lynch, Y. Furukawa, J. Griffin, H. Piwnica-Worms, C.M. Huang, and D.M. Livingston, Cell 58:1085-1095, 1989; and K. Mihara, X.R. Cao, A. Yen, S. Chandler, B. Driscoll, A.L. Murphree, A. TAng, and Y.K. Fung, Science 246:1300-1303, 1989). Although the mechanism of action of p110RB1 remains unknown, several lines of evidence suggest that it plays a role in the regulation of transcription. We now show that overexpression of p110RB1 causes repression of the adenovirus early promoter EIIaE and the promoters of two cellular genes, c-myc and RB1, both of which contain E2F-binding motifs. Mutation of the E2 element in the c-myc promoter abolishes p110RB1 repression. We also demonstrate that a p110RB1 mutant, which is refractory to cell cycle phosphorylation but intact in E1a/large T antigen-binding properties, represses EIIaE with 50- to 80-fold greater efficiency than wild-type p110RB1. These data provide evidence that hypophosphorylated p110RB1 actively represses expression of genes with promoters containing the E2F-binding motif (E2 element).

Adenoviridae↗
PubMed1992

Mechanisms of loss of heterozygosity in retinoblastoma.

Retinoblastoma (RB) tumors arise when both alleles of the RB1 gene are inactivated by two mutational events (M1 and M2). M1 can be an initial germline or somatic mutation; M2 is frequently loss of heterozygosity (LOH), which makes the cell homozygous or hemizygous for the original mutation. LOH is the major mechanism by which many cancers are initiated. To further delineate the mechanism of LOH, we screened a total of 37 RB tumors for LOH by Southern blot analysis. The tumors were from 17 bilaterally and 17 unilaterally affected patients. Nineteen of 30 informative tumors (63%) from 27 patients showed LOH. Proximal and distal flanking markers on chromosome 13 were informative in 13 tumors, allowing evaluation of the mechanisms by which LOH occurred. Mitotic recombination was implicated in 6 (46%) of the 13 tumors.

Blotting, Southern↗
PubMed1992

Polycystic ovary syndrome: lack of hypertension despite profound insulin resistance.

It has been hypothesized that insulin resistance and hyperinsulinemia contribute to the development of arterial hypertension. To further investigate this relationship, we compared arterial blood pressure in controls and women with polycystic ovary syndrome (PCO), an insulin-resistant state. Fourteen PCO women and 18 normal control women of similar age, body mass index, and race were studied. Plasma glucose and insulin levels were determined in an oral glucose tolerance test. The insulin sensitivity (SI) index was determined by the minimal model method. Systolic and diastolic blood pressure were measured by 24-h ambulatory monitoring. Left ventricular mass was assessed by echocardiography. The two groups had comparable fasting glucose levels, but the 2-h postload glucose was higher in PCO (8.0 +/- 0.5 vs. 5.6 +/- 0.3 mmol/L; P less than 0.001). Compared to controls, PCO women were significantly more insulin resistant by fasting insulin, 2-h insulin concentrations, and SI (28.3 +/- 6.7 vs. 68.3 +/- 10.0 min-1/nmol.mL; P less than 0.01). Average ambulatory systolic (121 +/- 2 vs. 118 +/- 2 mm Hg) and diastolic (76 +/- 2 vs. 73 +/- 2 mm Hg) blood pressures were similar for PCO and control women. No difference was found in left ventricular mass. Therefore, despite profound insulin resistance and hyperinsulinemia, women with PCO do not have increased arterial pressure or left ventricular mass.

Adult↗
PubMed1992

The retinoblastoma protein and the cell cycle.

Although mutations of the retinoblastoma gene (RB1) contribute to malignant progression in many types of tumor, the role of RB1 mutation in cancer initiation is highly restricted to the rare embryonic tumor, retinoblastoma. However, RB1 is expressed and its product, p110RB1, is regulated through the cell cycle in many tissues. This apparent paradox may be clarified by the emerging evidence that p110RB1 functions as a regulator of transcription of cell cycle genes. Tissue specific effects may be determined by the cellular proteins that interact with p110RB1, or by cell type-specific expression of target genes regulated by p110RB1.

Cell Cycle↗
PubMed1992

Differential kinetics of engraftment and induction of CD10 on human pre-B leukemia cell lines in immune deficient scid mice.

The sensitivity of the scid mouse model was assessed by comparing the growth of two pre-B acute lymphoblastic leukemia (ALL) cell lines, A1 and G2, established from patients at relapse. When cell numbers varying from 10(4) to 10(7) were injected intravenously into scid mice, advanced growth and dissemination of leukemia was observed at 10-12 weeks with the G2 cells. Bone marrow, spleen and thymus contained high levels of human leukemic cells and infiltration into lung, kidney, liver, and brain was observed. Two of three mice grafted with only 100 cells showed high levels of infiltration at 15 weeks, suggesting that 100 G2 cells was near the limiting cell number that could produce disseminated leukemia. With the A1 line, a minimum of 10(5) cells was needed to obtain dissemination to liver, lung, brain, and kidney; a low level of spleen infiltration occurred and thymus invasion was not observed. In vitro, both lines showed a density dependent growth in clonogenic assays but the cloning efficiency of the A1 line was 10-fold higher than for G2 cells. These results indicate that G2 and A1 lines have a dissimilar aggressiveness in vivo which does not correlate with clonogenic assay in vitro. Neither G2 nor A1 lines, growing in vitro, expressed CD10/CALLA on their surface, despite low levels of antigen on the freshly obtained relapse samples. Although A1 cells remained CD10-negative in the scid mice, G2 cells showed detectable levels of CD10, particularly on those cells found in the thymus. Several subclones of the G2 line were derived from isolated colonies in vitro; they were found to be CD10- in vitro, but to become CD10+ when proliferating into scid mouse thymus, suggesting the induction of CD10 by the murine microenvironment.

Animals↗
PubMed1992

Regions controlling hyperphosphorylation and conformation of the retinoblastoma gene product are independent of domains required for transcriptional repression.

Cell cycle-dependent phosphorylation appears to control the function of the retinoblastoma gene product, p110RB1. We have previously shown that both the N-terminal portion and the portion corresponding to exon 23 are important in the hyperphosphorylation of p110RB1. To gain further insight into the domains involved in these phosphorylations, we have created a series of mutations in the murine cDNA and investigated their effects on phosphorylation, protein conformation and transcription of genes controlled by an E2 element. Three series of p110RB1 constructs were made: (1) mutations and/or deletions in the cluster of potential p34cdc2 consensus sequences of exon 23, (2) deletions for the entire region C-terminal to the large T antigen (TAg)-binding domains or (3) mutations in eight potential p34cdc2 sites, including four in exon 23. Following transfections into COS cells, phosphorylation, TAg binding and protein conformation were evaluated. Constructs were also tested for their ability to repress transcription from the adenovirus early promoter. All mutant proteins bound to SV40 TAg. Mutation of Ser-781, Ser-787 and Ser-788 had no detectable effect on the phosphorylation pattern of p110RB1, producing both the fast-migrating, hypophosphorylated and slower migrating, hyperphosphorylated bands on SDS-PAGE gels. However, mutation or deletion of Ser-800 and Ser-804 resulted in proteins which failed to show the characteristic shift in molecular weight associated with the hyperphosphorylated form of p110RB1. A protein mutated only at Pro-805, the residue adjacent to Ser-804, behaved similarly to mutants with both Ser-800 and Ser-804 altered; mutation of Pro-801 had no effect on the mobility of the hyperphosphorylated species. While differences were seen in the ability of these proteins to be hyperphosphorylated, the wild-type function of repression of adenovirus early promoter activity was retained. These results are consistent with the large shift in apparent molecular weight of p110RB1 upon hyperphosphorylation being due to phosphorylation of Ser-804. Phosphorylation of this p34cdc2 consensus sequence and the subsequent conformational change in p110RB1 detected in denaturing gels is not necessary, however, for the phosphorylation-dependent modulation of p110RB1-TAg interaction.

Amino Acid Sequence↗
PubMed1991

Bone marrow from children in relapse with pre-B acute lymphoblastic leukemia proliferates and disseminates rapidly in scid mice.

Bone marrow samples from patients with pre-B acute lymphoblastic leukemia (pre-B ALL), either at diagnosis or at relapse, were transplanted into scid mice to determine whether these freshly obtained leukemic cells could proliferate in vivo and whether there were any differences in their in vivo growth characteristics. Cells from three patients who relapsed within 13 months of diagnosis proliferated rapidly in the murine bone marrow, spleen, and thymus, invaded peripheral organs, and resulted in morbidity and mortality of the animals within 4 to 16 weeks. Cells from two patients who relapsed 3.5 years after diagnosis grew much slower than the early relapse samples, taking up to 30 weeks to infiltrate the bone marrow of recipient mice. In contrast, leukemic cells were absent or were detected at low numbers in scid mice transplanted with cells obtained at diagnosis from three patients who have not yet relapsed. These results show an increased ability of leukemic cells from patients with aggressive lymphoblastic leukemia of poor prognosis to proliferate in scid mice.

Adolescent↗
PubMed1991

Normalization of left ventricular mass and associated changes in neurohormones and atrial natriuretic peptide after 1 year of sustained nifedipine therapy for severe hypertension.

Sixteen patients with severe hypertension were treated for 1 year with extended release nifedipine, during which time serial changes in left ventricular mass index and associated alterations in left ventricular systolic function, left ventricular filling, plasma renin activity, atrial natriuretic peptide and catecholamines were evaluated. Mean seated blood pressure (+/- SE) was significantly reduced from 200 +/- 8/122 +/- 3 to 144 +/- 5/89 +/- 2 mm Hg (p less than 0.0001) at 1 year. After 6 months, left ventricular mass index was significantly reduced by 19% from 121 +/- 8 to 96 +/- 7 g/m2 and this reduction was sustained at 1 year. Septal and posterior wall thickness were reduced from 13.4 +/- 0.1 to 11.2 +/- 0.04 mm and from 12.8 +/- 0.1 to 10.0 +/- 0.03 mm (p less than 0.001), respectively. The prevalence of left ventricular hypertrophy decreased from 63% to 25%. Left ventricular fractional shortening increased from 34 +/- 2% to 41 +/- 3% (p less than 0.05) and the relation between fractional shortening and end-systolic stress did not change. Over the year of sustained blood pressure reduction, the peak velocity of early filling increased from 57 +/- 3 to 63 +/- 4 cm/s (p = 0.07), peak velocity of late filling did not change and the ratio of late to early peak left ventricular filling velocity significantly decreased (p less than 0.05). Plasma atrial natriuretic peptide levels, markedly elevated at entry, decreased from 70 +/- 15 to 41 +/- 8 pg/ml at 1 year (p less than 0.05). Plasma renin activity and catecholamine levels were not altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗