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R A Phillips

Publications and source records attributed to R A Phillips.

At least 73 records · Page 4Linked to original sources
PubMed1995

Antigen-presenting cells for naive transgenic gamma delta T cells. Potent activation by activated alpha beta T cells.

The function of gamma delta T cells, particularly the minor population of circulating gamma delta T cells, remains unclear. To study these lymphoid gamma delta T cells, a transgenic SCID mouse containing the KN6 gamma delta TCR whose ligand is the TL gene product, T22b, was created. KN6-SCID mice contain a monoclonal population of naive KN6+ gamma delta T cells. Using these mice, we have studied the APC required for activation of KN6+ gamma delta T cells in vitro and in vivo. Analysis of an in vitro mixed lymphocyte response identified a hierarchy of potency for stimulation: dendritic cells = T cell blasts > B cell blasts > B cells > resting T cells. In contrast, in vivo, only alpha beta T cells fully activated KN6+ gamma delta T cells as measured by an increase in the number of splenic KN6+ cells, the development of blast morphology, and the development of proliferative anergy in the responding KN6+ cells. The strong stimulatory properties of C57BL/6J T cells appeared to depend on their having been activated by KN6-SCID alloantigens. T cells from (C57BL/6J x BALB/c)F1 mice, which are tolerant of KN6-SCID alloantigens, could not fully activate KN6+ cells. However, the F1 T cells could activate KN6+ cells if they were activated in vivo by the mitogen, staphylococcal enterotoxin B. A mixture of third party activated T cells plus T22b+ non-T cells only partially activated KN6+ cells, implying that activated T22b+ T cells are acting directly as stimulatory cells. Although the Ags recognized by gamma delta T cells are generally unknown, Ag presentation by activated alpha beta T cells may be an important method of activation.

Animals↗
PubMed1995

Direct transcriptional repression by pRB and its reversal by specific cyclins.

It was recently shown that the E2F-pRB complex is a negative transcriptional regulator. However, it was not determined whether the whole complex or pRB alone is required for repression. Here we show that pRB and the related protein p107 are capable of direct transcriptional repression independent of E2F. When fused to the DNA binding domain of GAL4, pRB or p107 represses transcription of promoters with GAL4 binding sites. Thus, E2F acts as a tether for pRB or p107 but is not actively involved in repression of other enhancers. This function of pRB maps to the pocket and is abrogated by mutation of this domain. This result suggests an intriguing model in which the pocket has a dual function, first to bind E2F and second to repress transcription directly, possibly through interaction with other proteins. We also show that direct transcriptional repression by pRB is regulated by phosphorylation. Mutations which render pRB constitutively hypophosphorylated potentiate repression, while phosphorylation induced by cyclin A or E reduces repression ninefold.

Base Sequence↗
PubMed1995

Anatomic structures at risk: combined subtalar and ankle arthrodesis with a retrograde intramedullary rod.

Retrograde intramedullary rodding from the calcaneus, through the talus, and into the tibia is currently an evolving procedure being used for salvage of severe foot/ankle deformity, arthritis, tumor, and instability. In this study, retrograde rodding was performed on six cadaver specimens. The specimens were then dissected to determine the subcalcaneal structures at risk and the optimal insertion point for the rod. This study elucidated the structures most at risk and showed the optimal insertion site to be at the junction of the sustentaculum tali and the body of the calcaneus.

Ankle Joint↗
PubMed1994

Significance of distal false lumen after type A dissection repair.

Fifty-eight patients underwent repair of acute type A dissection between 1986 and 1992. Follow-up aortogram, computed tomographic scan with contrast, magnetic resonance imaging scan, or a combination of these tests was available in 38 patients with preoperatively patent distal false lumens. All distal anastomoses were constructed with the open technique during a period of circulatory arrest. There were 25 suture and 13 intraluminal graft anastomoses. Patency of the distal false lumen was found in 47.3%. Use of the intraluminal graft for the distal anastomosis decreased patency, although not significantly (4/13, 30% versus 14/25, 56%; p = 0.14). The direction of flow into the false lumen was antegrade in 11 of 24 (45.8%) of sutured anastomoses and 0 of 9 intraluminal graft anastomoses (p < 0.01). Actuarial survival at 5 years for patients with closed distal false lumen was 95% +/- 4.8% versus 76% +/- 15% for patients with patency of the distal false lumen (p = not significant). Event-free survival at 5 years for both groups was 84% +/- 8.3% (closed false lumen) and 63% +/- 13.5% (patency of distal false lumen; p = not significant). This experience indicates that in the treatment of acute type A dissections, operative strategy and anastomotic technique play a role in reducing the incidence of patency and related complications of the distal false lumen.

Actuarial Analysis↗
PubMed1994

Persistent white coat hypertension.

Serial observations of clinic and ambulatory blood pressure monitoring are presented for a 60-year-old woman whose arterial blood pressure was unaffected by removal of a functioning parathyroid adenoma. A pattern of "white coat hypertension" first detected 8 years ago remains unchanged to the present.

Adenoma↗
PubMed1994

Characterization of the human RB1 promoter and of elements involved in transcriptional regulation.

The retinoblastoma gene (RB1) is a recessive oncogene implicated in a number of human tumors. Although the RB1 gene is expressed in most proliferating cells, there is considerable evidence for the transcriptional regulation of this gene. Therefore, we have performed a detailed analysis of the regulatory elements in the promoter of the human RB1 gene. Deletion analysis of the 5' upstream region determined the location of the basal promoter to be between -208 and -179 nucleotides relative to the translational start. This region contains essential binding sites for the transcription elements ATF and SP1 and potentially important sites for E2F and steroid hormone responsiveness but no TATA or CAAT boxes. Primer extension and RNase protection analysis identified two initiation sites at -176 and -128 base pairs, both downstream of the promoter. Cotransfection experiments revealed repression of the RB1 promoter by its protein product p110RB1. This repression has been mapped to the core promoter region containing the E2F-binding site; however, this site is not required for autorepression.

Activating Transcription Factors↗
PubMed1993

Gamma delta T cells differentiate into a functional but nonproliferative state during a normal immune response.

To obtain a homogeneous population of gamma delta T cells to investigate their role in an immune response, we have made a scid mouse doubly transgenic for rearranged gamma and delta genes. The receptor (KN6) encoded by these genes is specific for the major histocompatibility complex class I protein encoded by the T22b gene. This mouse contains high levels of transgenic gamma delta T cells in the spleen and thymus and no other T lymphocytes. Immunization of these KN6-scid (H-2d, TLd) mice with 10(7) C57BL/6J (abbreviated B6) (H-2b, TLb) spleen cells resulted in proliferation and activation of the gamma delta T cells in spleen and clearing of the allogeneic B6 lymphocytes. Subsequently, the majority of activated cells died by apoptosis and the remaining cells were anergic with regard to proliferation. The anergic cells did not respond to restimulation by B6 spleen cells in vitro or in vivo, and addition of exogenous interleukin 2 failed to restore the response to B6 cells. Cytotoxicity, a property of KN6+ cells during a primary stimulation, was no longer detectable in the proliferatively anergic cells. However, B6 spleen cells injected into mice primed 12 days previously were cleared with a much greater efficiency than on primary challenge and in an antigen-specific manner. We conclude that after exposure to antigen, gamma delta T cells rapidly proliferate into blasts; the majority of the blasts rapidly die, with the nonproliferating cells remaining in a highly active state for several weeks and able to initiate elimination of lymphoid cells bearing the TLb epitope.

Animals↗
PubMed1993

High frequency of normal DJH joints in B cell progenitors in severe combined immunodeficiency mice.

The severe combined immunodeficiency (scid) mouse has a defective V(D)J recombinase activity that results in arrested lymphoid development at the pro-B cell stage in the B lineage. The defect is not absolute and scid mice do attempt gene rearrangement. Indeed, approximately 15% of all scid mice develop detectable levels of oligoclonal serum immunoglobulin and T cell activity. To gain more insight into the scid defect and its effect on V(D)J rearrangement, we analyzed DJH recombination in scid bone marrow. We determined that DJH structures are present in scid bone marrow and occur at a frequency only 10-100 times less than C.B-17+/+. The scid DJH repertoire is limited and resembles fetal liver DJH junctions, with few N insertions and predominant usage of reading frame 1. Moreover, 70% of the DJH structures were potentially productive, indicating that normal V(D)J recombinants should be arising continually.

Animals↗
PubMed1993

Interleukin-7 responsiveness of B220+ B cell precursors from bone marrow decreases in aging mice.

Using short-term culture assays to quantify the activity of B220+ B cell progenitors from bone marrow of young and old mice, we observed a decrease with age in the ability of B220+ cells in bone marrow to proliferate in IL-7. Dose-response curves showed no difference between young and old mice in the amount of IL-7 required to stimulate B220+ cells. However, the B220+ cells from the bone marrow of old donors (> 20 weeks) contained two- to fivefold fewer cells responsive to IL-7 than the identical cell population isolated from young donors. Similar results were obtained with mice up to 48 weeks of age from three different strains, BALB/c, C57BL/6, and C.B-17. These data provide evidence for a small, but reproducible, age-associated decrease in B cell production.

Aging↗
PubMed1993

Speculations on the roles of RB1 in tissue-specific differentiation, tumor initiation, and tumor progression.

Studies of retinoblastoma clearly identify mutation of the RB1 gene on chromosome 13 as the primary cause of this cancer. However, all retinoblastoma tumors have an abnormal karyotype (1, 2) indicating the presence of additional mutations and suggesting that mutation of both RB1 alleles is insufficient for development of retinoblastoma. In addition, analysis of RB1 expression and of RB1 mutations in different tumors leads to the following dilemma: while the RB1 gene product, p110RB1, is expressed in most dividing cells, germline mutations inactivating the function of p110RB1 predispose primarily to retinoblastoma and to a lesser extent to osteosarcoma, but do not predispose to cancer in general. However, many tumors contain somatic mutations that disrupt RB1 function. Thus, we are faced with the unusual situation in which germline mutations in the RB1 gene predispose to a very limited set of cancers, but somatic mutations in RB1 appear to contribute to malignancy in many tissues. We propose that the role of the RB1 gene is to maintain the cells in a stable, quiescent state required for terminal differentiation and that the effect of RB1 mutations in different tissues depends on the pattern of differentiation in that tissue. In tissues where differentiation follows a linear process from undifferentiated precursors to fully differentiated cells, loss of RB1 function during early stages of differentiation may lead to uncontrolled growth and the development of cancer. On the other hand, in cell renewal systems where cell number is usually maintained by a process of programmed cell death (PCD) or apoptosis, loss of RB1 function may lead to cell death.

Animals↗
PubMed1993

Etiology, pathophysiology, and treatment of left ventricular hypertrophy: focus on severe hypertension.

Left ventricular hypertrophy (LVH), a common finding in hypertensive patients, has emerged as one of the most potent risk factors for future cardiovascular mortality in patients with hypertension. LVH is associated with multiple physiologic abnormalities, which may account for the increased risk. These include coronary perfusion abnormalities such as reduced coronary flow reserve, altered coronary flow autoregulation, subendocardial hypoperfusion, and abnormal left ventricular (LV) diastolic function. Although abnormalities of LV diastolic function are more common in LVH, they may occur early in the course of the disease. There may be a threshold of average awake ambulatory blood pressure (BP), 130/85 mm Hg, below which neither diastolic abnormalities nor LVH is detected. The reasons for reduced reserve coronary flow reserve are complex and include structural and functional abnormalities of myocardial blood vessels such as reduced capillary density, reduced luminal diameter of intramyocardial small arteries, and increased vascular tone, possibly as a result of factors such as abnormal endothelium-dependent relaxation. Preliminary data suggest that regression of LVH is associated with improved survival. Severe hypertensive patients would be expected to achieve the greatest benefit, because, if left untreated, this group has nearly 20% mortality within 2 years. To evaluate the effect of nifedipine gastrointestinal therapeutic system (GITS) on LV mass, 16 patients with initial diastolic BP > 120 mm Hg were treated for 1 year with either monotherapy or in combination with a thiazide diuretic. Because it has not been unequivocally shown that changes in LV mass have physiologic benefit, associated alterations in LV systolic function, LV filling, plasma renin activity, atrial natriuretic peptide, and catecholamines were also evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

A bipartite nuclear localization signal in the retinoblastoma gene product and its importance for biological activity.

The retinoblastoma gene product, p110RB1, appears to regulate cell growth by modulating the activities of nuclear transcription factors. The elements that specify the transport of p110RB1 into the nucleus have not yet been explored. We now report the identification of a basic region, KRSAEGGNPPKPLKKLR, in the C terminus of p110RB1, which has sequence similarity to known bipartite nuclear localization signals (NLSs). A two-amino-acid mutation introduced into this putative NLS [to give mutant NLS(NQ)] or deletion of the entire NLS (delta NLS) abrogated exclusive nuclear localization, yielding proteins which were distributed either equally throughout the cell or predominantly in the cytoplasm. A mutant protein [NLS(NQ)/delta 22] containing both the mutated NLS and a deletion of exon 22, previously shown to disrupt the interaction of p110RB1 with several cellular transcription factors and oncoproteins, accumulated only in the cytoplasm. When fused to the C terminus of Escherichia coli beta-galactosidase, the RB1 NLS directed this protein to the nucleus, indicating that the motif is not only necessary but also sufficient for nuclear transport. Neither NLS(NQ) nor delta NLS was hyperphosphorylated in vivo, but both retained their abilities to interact, in vitro, with simian virus 40 large T antigen, adenovirus E1a, and the cellular transcription factor E2F. When transfected at multiple copy number, the NLS mutant alleles displayed reduced biological activity, measured by inhibition of growth of the osteogenic sarcoma cell line Saos-2, which has no wild-type RB1. Naturally occurring mutations and deletions in exon 25 of RB1 which disrupt the NLS may lead to partial or complete inactivation of p110RB1 and may be responsible for some retinoblastoma and other tumors.

Amino Acid Sequence↗
PubMed1993

Anticardiolipin antibodies in ischaemic heart disease: marker or myth?

OBJECTIVES: To assess the incidence and significance of anticardiolipin antibodies after myocardial infarction and in unstable angina. DESIGN: A prospective study of all patients under 60 admitted to the coronary care unit over a 12 month period with a diagnosis of acute myocardial infarction who were followed up for a further 12 months. Patients admitted with unstable angina were similarly assessed but not followed up. Anticardiolipin antibody concentrations were compared with those of age matched controls. SETTING: A district general hospital. PATIENTS: 307 patients with acute myocardial infarction and 160 patients with unstable angina. RESULTS: Anticardiolipin antibody concentrations in the two patient groups did not differ significantly from those in the control groups. Antibody concentrations were not related to a history of angina or myocardial infarction nor were they related to subsequent cardiovascular complications. CONCLUSION: This study shows no significant association between anticardiolipin antibody concentrations and either myocardial infarction or unstable angina.

Angina, Unstable↗