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Biomedical subjects

I Beckman

Publications and source records attributed to I Beckman.

At least 19 recordsLinked to original sources
PubMed1997

The T cell in the ageing individual.

Aged persons frequently manifest declining parameters of those immune functions which protect the young against disease. Longitudinal studies are beginning to show that number, type and function of T cells may be associated with longevity, morbidity and mortality in free-living elderly humans. Multi-faceted alterations in the ability of T cells from old donors to respond to stimulation are being dissected, and pathways which are compromized in the elderly compared to the young are being defined. Successful immune responses depend upon waves of rapid and extensive clonal expansion to combat primary infection, followed by death of most T cells, survival of memory cells and their later reactivation and further expansion. This implies that the finite replicative potential of T cells might impose a critical limiting factor on the maintenance of immune responses in the face of thymic involution and drastically reduced capacity to generate new naive T cells. This type of 'clonal exhaustion' can readily be studied in vitro using human T cell clones and the findings can be applied to the in vivo situation. Understanding the processes of replicative senescence in such in vitro models may shed light not only on some of the underlying mechanisms of immunosenescence but also in situations of chronic antigenic stimulation in vivo. Moreover, it might begin to indicate how the system could be manipulated on the one hand to prevent or reverse T cell senescence without nullifying the control mechanisms of tumor suppression, and on the other hand, to reconstitute possibly faulty suppression, for example in autoimmune disease.

Adult↗
PubMed1997

High incidence of interleukin 10 mRNA but not interleukin 2 mRNA detected in human breast tumours.

Despite the presence of a lymphocytic infiltrate in solid cancers, the failure for tumour growth to be contained suggests an inadequate immune response to the tumour. Poor cytotoxicity exerted by tumour-infiltrating lymphocytes (TILs) against tumour cells in vitro, combined with continued tumour growth in vivo, suggests deficiencies in TIL function or numbers. Various theories have been postulated to explain how tumour cells may escape immunosurveillance and control. One of the many hypotheses is the failure of production of cytokines, which are necessary for T cells to mediate their function. Thus, the expression of cytokine mRNA in human breast tumour sections was investigated by reverse transcriptase polymerase chain reaction (RT-PCR) with cytokine-specific primers. A relatively consistent finding was detection of interleukin (IL) 10 mRNA among the tumours. No IL-2 and little IL-4 mRNA was detected in the tumours. IL-6 and IL-10 mRNA was detected in only one and two of the normal breast tissues respectively. IL-2, IL-4 and tumour necrosis factor (TNF)-alpha mRNA was not detected in any of the normal breast tissues. The reduced function of TILs may be related to IL-10, which has known inhibitory effects on T-cell activation.

Adult↗
PubMed1996

Spiral CT during arterial portography.

Spiral computed tomography (CT) performed during arterial portography offers several advantages compared with portographic studies based on conventional CT technique. Because all hepatic images are derived from a volume data set acquired during a single 24-32-second breath hold timed to coincide with the phase of peak hepatic enhancement, motion artifacts and section misregistration are eliminated and high liver-to-lesion attenuation value differences are present on all sections. These factors, in conjunction with the ability to retrospectively acquire thin, overlapping axial sections, result in improved lesion detection. The ability to produce high vein-to-liver attenuation value differences and two-dimensional multiplanar reconstructions simplifies the identification of hepatic segments and therefore lesion localization. A limitation of all CT portographic methods is the frequent occurrence of nontumorous perfusion defects that, in most cases, demonstrate characteristic locations and appearances. Performing delayed CT following portography is one method by which such pseudolesions may be characterized and differentiated from focal pathologic entities.

Artifacts↗
PubMed1995

Transcranial Doppler sonography. Part 1. Principles, technique, and normal appearances.

Transcranial Doppler sonography is a noninvasive technique that uses a 2-MHz, pulsed Doppler transducer to measure the velocity of blood flow within the circle of Willis and vertebrobasilar system through regions of temporal calvarial thinning or through the orbits or foramen magnum. By using spectral analysis of the Doppler frequency shifts from insonated red blood cells moving through a preselected arterial sample volume, transcranial Doppler calculates and displays the peak systolic and diastolic velocity, the mean velocity, and the pulsatility index of blood flow within the interrogated vessel. Vessel identification is based on standard criteria, including the cranial window used, transducer position, depth of sample volume, direction of blood flow, relationship to the terminal internal carotid artery, and response to common carotid artery compression. Diagnoses made with transcranial Doppler sonography are based on the detection of increased or decreased blood flow velocity, absence of blood flow, or changes in pulsatility.

Blood Flow Velocity↗
PubMed1995

Transcranial Doppler sonography. Part 2. Evaluation of intracranial and extracranial abnormalities and procedural monitoring.

Transcranial Doppler sonography can be used to evaluate a spectrum of intracranial and extracranial vascular abnormalities. It is of proved value in the detection and follow-up of vasoconstriction caused by subarachnoid hemorrhage and can be used to demonstrate significant stenosis or occlusion of basal intracranial arteries and coexisting routes of collateral circulation. Transcranial Doppler sonography can play an important role in the determination of brain death and can be used to identify the nidus of an arteriovenous malformation, along with its major routes of supply and drainage. The technique may provide insights into cerebral hemodynamics following trauma, stroke, or migraine. Use of transcranial Doppler sonography enables a rapid, noninvasive diagnosis of the subclavian steal syndrome, and it is a valuable adjunct to duplex carotid sonography for determining the effect of atherosclerotic lesions of the internal carotid artery on cerebral hemodynamics. In the operating room or angiographic suite, transcranial Doppler sonography can be used to monitor patients undergoing surgical, interventional, or diagnostic procedures for the development of cerebrovascular complications.

Brain Death↗
PubMed1995

Age-related defects in CD2 receptor-induced activation in human T-cell subsets.

It is well documented that the proliferative capacity of T cells declines with advancing age. There are, however, conflicting data as to the role of the accessory cell and whether or not this loss in responsiveness extends to all T-cell stimuli and to all T cells. We report here on the capacity of subpopulations of peripheral blood CD4+ T cells from the healthy aged to proliferate in response to anti-CD2 receptor-induced activation in the complete absence of accessory cells by using various exogenous cofactors as second signals. These costimulatory factors included phorbol 12-myristate 13-acetate (PMA), interleukin (IL)-1, IL-2, IL-6 and IL-7 and the monoclonal antibodies, anti-CD28 and anti-CD44. Under these conditions, the proliferative responsiveness of CD4+CD45RO+ T cells from the aged was found to be comparable to young control cells for all stimuli tested, except anti-CD2 plus IL-7. This suggests that signal transduction pathways involving CD2, except IL-7-mediated events, are essentially intact in 'old' memory CD4+ T cells. On the other hand, several cofactors, namely IL-2, IL-6, IL-7 and to a lesser extent IL-1 beta and PMA, failed to support adequately CD2-induced activation in 'old' CD4+CD45RA+ T cells suggesting severe and multiple signalling deficiencies in this subset.

Aged↗
PubMed1994

Cytokine receptor expression in leukaemic cells.

Cytokines have been postulated to play important roles in tumour biology and in the host response to tumours, and a number of therapeutic modalities involving cytokines have been proposed. If patients are to be treated with cytokines, or cytokine inhibitors, it will be important to determine the potential for direct action of the cytokine on the tumour cells. In this study, a high-sensitivity immunofluorescence technique is used to determine the expression of a number of cytokine receptors on a total of 115 leukaemic samples. The results show that many leukaemic samples express low levels of cytokine receptors, and that malignancies of a particular type are heterogeneous with respect to receptor expression. In vitro culture experiments show, as expected, that receptor expression is a necessary but not sufficient requirement for responsiveness to cytokines. The cytokine receptor phenotype may provide useful additional clinical and prognostic information, and should be determined particularly for patients undergoing treatment with cytokines or cytokine inhibitors.

Acute Disease↗
PubMed1994

Differential expression and regulation of cytokine mRNAs in normal human CD45R T cell subsets.

Cytokine mRNA expression was analyzed by reverse transcriptase (RT)/PCR in extensively purified normal peripheral CD4+CD45R T cell subsets. Both CD45RA+ and CD45 RO+ populations produced mRNAs for interleukin (IL)-2, IL-2 receptor (alpha chain), IL-6 receptor and tumour necrosis factor (TNF)-beta within 3-4 h of activation. Whilst IL-3 and RANTES were also expressed in both subsets, CD45RO+ cells were clearly the major producers of these cytokines. In contrast, mRNA transcripts for IL-1 alpha, IL-4, IL-5, IL-6, IL-10, interferon gamma (IFN-gamma) and the T cell receptor for IL-1 were almost exclusively induced in CD45RO+ T cells. A population of CD4+ T cells co-expressing intermediate levels of both CD45RA and CD45RO, namely CD45RA+/CD45RO+, appeared to be the major producers of IL-6. Addition of cycloheximide (CHx) 4 h after T cell activation resulted in substantial superinduction of IL-2 mRNA in the CD4+CD45RO+ population but had little effect on CD4+CD45RA+ cells. Taken together, these results show that normal CD4+CD45R T cell subsets exhibit distinct cytokine mRNA profiles and that these differ from the patterns displayed by Th1 and Th2 type T helper clones. Furthermore, they suggest for the first time that IL-2 mRNA turnover is differentially regulated in CD45R T cell subsets.

Adult↗
PubMed1994

Endothelial serpins--protectors of the vasculature?

Vascular damage, initiated by host inflammatory cells, is a component of the pathophysiology of many acute and chronic inflammatory disorders. Neutrophil-mediated tissue damage is mediated primarily by proteinases, particularly elastase and cathepsin G. In this study we have identified endothelial binding of two key serine proteinase inhibitors (serpins), alpha 1-antitrypsin, the inhibitor of elastase, and alpha 1-antichymotrypsin, the inhibitor of cathepsin G. These serpins are shed from the endothelium into the supernatant when neutrophils adherent to the endothelium are activated. Endothelium activated by lipopolysaccharide (LPS) augments this process. Serpin-proteinase complexes activate neutrophils and induce further cytokine release, thereby amplifying inflammatory processes. Strategies aimed at preventing endothelial serpin depletion may help minimize vascular damage during inflammation.

Adult↗
PubMed1993

A comprehensive analysis of peripheral blood lymphocytes in healthy aged humans by flow cytometry.

This study used a panel of mAb and multiparameter flow cytometry to assess the composition of PBL from healthy aged individuals. The results showed that while total lymphocyte numbers altered only marginally in the aged (> or = 70 years) there were significant changes in the distribution of various sub-populations; for example, there were lower numbers of CD3+ and CD8+ cells, and higher numbers of CD16+ (NK) cells. As a direct result of these changes the numbers of CD2+ cells remained unchanged in the aged compared with young adult controls (18-25 years). The number of CD4+ T cells expressing CD45RO isoform (memory cells) exceeded the number of CD4+CD45RA+ (naive) cells in aged donors, whereas the converse was true for young donors. In addition, associated with this increase in CD45RO+ cells, the aged showed an expanded population of CD45RO+ T cells displaying low surface levels of CD45RO. These data suggest that shifts in the distribution of regulatory T cell subsets may play a role in age-related changes in immune response.

Adolescent↗
PubMed1993

Age-related changes in the expression of IL-2 and high-affinity IL-2 binding sites.

T cell responsiveness to in vitro stimulation is severely diminished in the aged. Recent studies would suggest that this may be due, at least in part, to a reduction in interleukin 2 (IL-2) secretion and high-affinity IL-2 receptor (HA-IL-2R) expression. In this report we confirm and extend these studies to show that the fall in IL-2 production is not due to reduced numbers of IL-2 mRNA producing T cells but rather to a decline in the relative amount of IL-2 mRNA expressed per cell. Although we found an age-related reduction in the number of high-affinity binding sites on phytohaemagglutinin-activated T cell blasts by ligand-binding studies, we did not observe alterations in the number of cells that expressed both chains of the HA-IL-2R by two-colour immunofluorescence using monoclonal antibodies specific for p55 (alpha) chain and p75 (beta) chain. However, we did observe a substantial diminution in the number of activated T cells expressing p55 alone in the aged. Given that IL-2 upregulates p55 expression and is involved in the formation of HA-IL-2R, our results suggest that defective IL-2 expression is the primary lesion in age-related T cell senescence.

Adult↗
PubMed1992

Silent rectal perforation after endoscopic polypectomy: CT features.

A case of silent extraperitoneal rectal perforation secondary to colonoscopic polypectomy is presented. Computed tomography (CT) demonstrated pathways of gas diffusion from the perirectal site to different compartments of the retroperitoneum, to the mediastinum and peritoneum.

Aged↗
PubMed1992

Age-related changes in the expression of T cell activation antigens following phytohaemagglutinin stimulation.

The role of accessory cells (AC) in the temporal expression of several key T-cell-activation-associated antigens has been studied in healthy aged subjects. Compared to responses seen in young adults, phytohaemagglutinin (PHA) induced weak proliferation in peripheral blood mononuclear cells from the aged and lower numbers of T cells expressing CD71, CD25, CD38 or HLA-DR. T cell responses to the monoclonal antibody OKT3, however, were normal. Whereas HLA-DR+ T cell numbers could be increased by raising the AC content (up to 50%) in cultures comprising purified T cells and graded numbers of autologous AC, CD25+ T cell numbers remained largely unaltered. Co-stimulation with PHA + phorbol myristate acetate in the absence of AC restored both proliferation and CD25 expression in the aged. These results indicate that T cells from the healthy aged show selective deficiencies in their capacity to respond to mitogenic stimuli and suggest that impaired PHA responsiveness is due, at least in part, to defective AC-derived signals.

Aged↗
PubMed1991

Age-related changes in the activation requirements of human CD4+ T-cell subsets.

In agreement with previous studies, we found that the proliferative response of unfractionated T-cells to phytohaemagglutinin (PHA) was severely impaired in healthy aged individuals (70-85 years). On the other hand, we did not observe significant differences between aged and young adults in T-cell responsiveness to mab OKT3 (anti-CD3). PHA responses in "old" T-cells could be substantially improved, however, by the addition of recombinant interleukin-2 (rIL-2) or KOLT2 (anti-CD28 mab). When individual CD4+ T-cell subpopulations were isolated from young and old donors and stimulated with PHA in the presence of autologous accessory cells, age-related deficiencies were seen in both CD4+CD45RA+ (naive) and CD4+CD45RO+ (memory) cell populations. Further analysis using a panel of coactivators in cultures depleted of accessory cells identified specific abnormalities in the CD2 or alternate pathway of T-cell activation. These were predominantly seen in CD4+ naive T-cells. The capacity of rIL-2, KOLT2, and PMA to restore, at least partially, T-cell responsiveness in the aged suggests a defect(s) in an early signal transduction mechanism.

Adult↗
PubMed1990

T cell activation in the elderly: evidence for specific deficiencies in T cell/accessory cell interactions.

We studied T cell activation in the healthy aged (greater than 70 years) by examining lymphocyte proliferative responses to various mitogenic stimuli in accessory cell (AC)-dependent and AC-independent systems. Results show that despite a near normal response to the anti-CD3 monoclonal antibody (mAb) OKT3, peripheral blood mononuclear cells (PBM) from the elderly exhibit a profound reduction in phytohaemagglutinin (PHA)-responsiveness (approximately 30% of young adults). This deficit becomes even more severe at suboptimal doses of PHA. Adding exogenous interleukin-2 (IL-2) or pretreating the AC population with gamma interferon (IFN-gamma) returns the level of proliferation to that seen with young adults. Furthermore, replacing "old" AC with AC from young adults or with U937 (a monocytic cell line) in T cell/AC cell-mixing experiments restores PHA-responsiveness in 70% of cases. On the other hand, AC from the aged fully support PHA responses in T cells from young adults. In AC-depleted cultures, purified T cells from the aged respond normally to the co-mitogenic stimuli, PHA + PMA. Taken together, these results suggest that the age-associated diminution in PHA-responsiveness is due, at least in part, to specific deficiencies in T cell/AC communication.

Aged↗
PubMed1990

Intra-aortic counterpulsation balloon pumps: CT appearance.

Intra-aortic counterpulsation balloon pumps (ICBP) used in the setting of cardiogenic shock or high risk cardiac surgery, have been identified on chest films in the inflated state during diastole (1). We report characteristic computed tomography (CT) findings of an inflated ICBP, discuss its radiographically identified complications, and suggest that the presence of this device should be excluded before suspecting other etiologies for intra-aortic gas.

Counterpulsation↗