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Biomedical subjects

A English

Publications and source records attributed to A English.

At least 19 recordsLinked to original sources
PubMed2001

In multiple myeloma, only a single stage of neoplastic plasma cell differentiation can be identified by VLA-5 and CD45 expression.

The nature of the proliferating fraction in myeloma is still not known and understanding the characteristics of this fraction is central to the development of effective novel therapies. However, myeloma plasma cells typically show a very low rate of proliferation and this complicates accurate analysis. Although the level of CD45 and/or VLA-5 has been reported to identify proliferating 'precursor' plasma cells, there are discrepancies between these studies. We have therefore used a rigorous sequential gating strategy to simultaneously analyse cycle status and immunophenotype with respect to CD45, VLA-5 and a range of other integrin molecules. In 11 presentation myeloma patients, the proliferative fraction was distributed evenly between CD45+ and CD45- cells, however, cycling plasma cells were consistently VLA-5-. There was close correlation between the expression of VLA-5 and a range of other integrin molecules (CD11a, CD11c, CD103), as well as the immunoglobulin-associated molecules CD79a/b (Spearman, n = 10, P < 0.0001). In short-term culture, cells that were initially VLA-5-showed increasing VLA-5 expression with time. However, simultaneous analysis of the DNA-binding dye 7-amino-actinomycin D demonstrated that this was not as a result of differentiation, as VLA-5+ plasma cells were all non-viable. This was confirmed in freshly explanted plasma cells from nine patients. Discrete stages of plasma cell differentiation could not be distinguished by the level of CD45 or VLA-5 expression. The results indicate that there is a single stage of plasma cell differentiation, with the phenotype CD38+CD138+VLA-5-. These findings support the hypothesis that neoplastic bone marrow plasma cells represent an independent, self-replenishing population.

Antigens, CD↗
PubMed2000

The interleukin-6 receptor alpha-chain (CD126) is expressed by neoplastic but not normal plasma cells.

Interleukin-6 (IL-6) is reported to be central to the pathogenesis of myeloma, inducing proliferation and inhibiting apoptosis in neoplastic plasma cells. Therefore, abrogating IL-6 signaling is of therapeutic interest, particularly with the development of humanized anti-IL-6 receptor (IL-6R) antibodies. The use of such antibodies clinically requires an understanding of IL-6R expression on neoplastic cells, particularly in the cycling fraction. IL-6R expression levels were determined on plasma cells from patients with myeloma (n = 93) and with monoclonal gammopathy of undetermined significance (MGUS) or plasmacytoma (n = 66) and compared with the levels found on normal plasma cells (n = 11). In addition, 4-color flow cytometry was used to assess the differential expression by stage of differentiation and cell cycle status of the neoplastic plasma cells. IL-6R alpha chain (CD126) was not detectable in normal plasma cells, but was expressed in approximately 90% of patients with myeloma. In all groups, the expression levels showed a normal distribution. In patients with MGUS or plasmacytoma, neoplastic plasma cells expressed significantly higher levels of CD126 compared with phenotypically normal plasma cells from the same marrow. VLA-5(-) "immature" plasma cells showed the highest levels of CD126 expression, but "mature" VLA-5(+) myeloma plasma cells also overexpressed CD126 when compared with normal subjects. This study demonstrates that CD126 expression is restricted to neoplastic plasma cells, with little or no detectable expression by normal cells. Stromal cells in the bone marrow microenvironment do not induce the overexpression because neoplastic cells express higher levels of CD126 than normal plasma cells from the same bone marrow in individuals with MGUS. (Blood. 2000;96:3880-3886)

Aged↗
PubMed2000

A monoclonal antibody against the 66-kDa protein expressed in mouse spleen and thymus inhibits Ly-6A.2-dependent cell-cell adhesion.

The Ly-6 locus encodes several cell surface proteins of 10-12 kDa. Some members of this multigene family may function in cell signaling and/or cell adhesion processes. T lymphocytes overexpressing Ly-6A.2 (one member of the Ly-6 gene family) protein homotypically aggregate when cultured in vitro. Further analysis of this homotypic aggregation suggests that Ly-6A.2 participates in cell-cell adhesion. These observations indicated the presence of a Ly-6 ligand(s) on the surface of lymphoid cells. In this study we report generation of a hamster mAb, 9AB2, that blocks Ly-6A.2-dependent cell-cell adhesion. The 9AB2 Ab recognizes a 66-kDa glycoprotein with unique tissue expression. The 9AB2 mAb does not bind Ly-6A.2, but coimmunoprecipitates Ly-6A.2 molecule. Moreover, 9AB2 Ag-expressing thymocytes specifically bind to Chinese hamster ovary cells overexpressing Ly-6A.2 protein, and this binding is specifically blocked by 9AB2 and anti-Ly-6A.2 Abs. These results suggest that the 66-kDa protein recognized by 9AB2 mAb is the putative ligand for Ly-6A.2.

3T3 Cells↗
PubMed2000

Reproductive health services for adolescents. Critical legal issues.

The contemporary legal and policy environment has increased the challenges associated with providing health care services to the adolescent population. The issue of reproductive health care services is particularly intense because of the controversial nature of services for contraception and abortion. As the debates continue, one must remember the background against which they are occurring. The current legal framework, developed over nearly 40 years, enables adolescents who are minors to give their own consent for care in numerous circumstances and provides them with a significant level of confidentiality protection, particularly for reproductive health services. Laws have been enacted to expand adolescents' financial access to health care, through targeted publicly funded service programs and expanded health insurance coverage. This background provides the foundation for addressing the current challenges and for protecting and expanding adolescents' access to care.

Abortion, Induced↗
PubMed2000

Dynamics of meningococcal long-term carriage among university students and their implications for mass vaccination.

In the 1997-98 academic year, we conducted a longitudinal study of meningococcal carriage and acquisition among first-year students at Nottingham University, Nottingham, United Kingdom. We examined the dynamics of long-term meningococcal carriage with detailed characterization of the isolates. Pharyngeal swabs were obtained from 2,453 first-year students at the start of the academic year (October), later on during the autumn term, and again in March. Swabs were immediately cultured on selective media, and meningococci were identified and serologically characterized. Nongroupable strains were genetically grouped using a PCR-based assay. Pulsed-field gel electrophoresis was used to determine the link between sequential isolates. Of the carriers initially identified in October, 44.1% (98 of 222) were still positive later on in the autumn (November or December); 57.1% of these remained persistent carriers at 6 months. Of the index carriers who lost carriage during the autumn, 16% were recolonized at 6 months. Of 344 index noncarriers followed up, 22.1% acquired carriage during the autumn term and another 13.7% acquired carriage by March. Overall, 43.9% (397 of 904) of the isolates were noncapsulated (serologically nongroupable); by PCR-based genogrouping, a quarter of these belonged to the capsular groups B and C. The ratio of capsulated to noncapsulated forms for group B and C strains was 2.9 and 0.95, respectively. Sequential isolates of persistent carriers revealed that individuals may carry the same or entirely different organisms at different times. We identified three strains that clearly switched their capsular expression on and off at different times in vivo. One student developed invasive meningococcal disease after carrying the same organism for over 7 weeks. The study revealed a high rate of turnover of meningococcal carriage among students. Noncapsulated organisms are capable of switching their capsular expression on and off (both ways) in the nasopharynx, and group C strains are more likely to be noncapsulated than group B strains. Carriage of a particular meningococcal strain does not necessarily protect against colonization or invasion by a homologous or heterologous strain.

Carrier State↗
PubMed2000

Financing adolescent health care: the role of Medicaid and CHIP.

Financing health care for adolescents involves a combination of public and private sources of payment and, in the public sector, a combination of insurance coverage and categorical programs. In recent years, the importance of health insurance coverage has increased along with the potential for insuring more adolescents. Medicaid and the new State Children's Health Insurance Program (CHIP) offer numerous options for reducing the proportion of uninsured adolescents and for increasing adolescents' access to necessary health care. This article explores the potential of Medicaid and CHIP for meeting adolescents' needs, the extent to which they have done so already, and the gaps or missing links that remain. It also reviews issues that cut across funding sources related to managed care, consent, and confidentiality.

Adolescent↗
PubMed1999

Distribution of myeloma plasma cells in peripheral blood and bone marrow correlates with CD56 expression.

There is a wide variation in the degree of marrow and blood involvement between patients with multiple myeloma. Both of these parameters are known to be highly significant prognostic factors, and the differences between patients may be due to variable expression of adhesion molecules. To test this we used three-colour flow cytometry to study three adhesion molecules associated with myeloma, namely CD38, CD56 and CD138. The level of expression of these molecules was compared with the distribution of myeloma plasma cells in bone marrow (n=59) and peripheral blood (n=26) in patients at presentation or relapse. The extent of marrow infiltration on the trephine biopsy correlated inversely with CD56 expression (Mann-Whitney U Test, P=0.022); there was no difference in CD38 or in CD138 expression. CD56 expression also correlated inversely with the number of circulating plasma cells (linear regression, R2=0.4268, slope=-0.58, P=0.0003). Peripheral blood plasma cell numbers correlated weakly with bone marrow plasmacytosis, and inversely with CD38 expression. The level of CD56 expression by neoplastic plasma cells was assessed in 37 patients over a median of 11 months (range 6-25). There was no significant change in expression (Wilcoxon Signed Rank, P=0.6271). We conclude that plasma cell CD56 expression is constant over the course of the disease; unlike CD138 expression, it is significantly linked to the degree of both bone marrow and peripheral blood involvement.

Bone Marrow↗
PubMed1999

The PNH phenotype cells that emerge in most patients after CAMPATH-1H therapy are present prior to treatment.

Paroxysmal nocturnal haemoglobinuria (PNH) cells are deficient in glycosylphosphatidylinositol (GPI) linked antigens due to a somatic mutation of the PIG-A gene in a haemopoietic stem cell. It appears that a PNH clone reaches detectable proportions only when there is selection in its favour. GPI-deficient T lymphocytes have been identified in patients treated with CAMPATH-1H, a monoclonal antibody against the GPI-linked CD52 molecule. CAMPATH-1H selects for cells that are deficient in CD52 (such as PNH-like cells) promoting the development of a PNH-like clone (analogous to PNH). We report that 10/15 patients with chronic lymphocytic leukaemia developed PNH-like lymphocytes after therapy with CAMPATH-1H. The remaining five patients developed no PNH-like cells at any stage, including one patient who received 12 weeks of therapy. The inactivating PIG-A mutation has been identified in one patient. This mutation was detectable by an extremely sensitive mutation-specific PCR-based analysis in the patient's mononuclear cells prior to CAMPATH-1H therapy. The frequency and phenotype of GPI-deficient lymphocytes after CAMPATH-1H and the detection of a PIG-A mutation in the lymphocytes prior to CAMPATH-1H therapy indicated that such mutations were present in a very small proportion of cells prior to selection in their favour by CAMPATH-1H. This suggests that a large proportion of individuals have cells with PIG-A mutations that are not detectable by flow cytometry and thus may have the potential to develop PNH.

Adult↗
PubMed1999

Legal issues in reproductive health care for adolescents.

Adolescents need reproductive and sexuality-related health care. State and federal laws affect consent, confidentiality, and payment for services. State minor consent laws allow minors to consent based on the minor's status or the services sought. State and federal laws affect confidentiality of health information generally as well as programs for specific services, such as family planning or drug and alcohol abuse treatment. Medicaid, the new State Children's Health Insurance Program, and categorical funding programs are important funding sources. Adolescents' ability to use these sources for confidential reproductive and sexuality-related services is evolving. However, possible changes in federal law and the transition to managed care in both public and private insurance present significant challenges they may face in the future.

Abortion, Legal↗
PubMed1998

CD4+ T cells mature in the absence of MHC class I and class II expression in Ly-6A.2 transgenic mice.

The TCRs expressed on T lymphocytes recognize foreign peptides bound to MHC molecules. This reactivity is the basis of specific immune response to the foreign Ag. How such specificities are generated in the thymus is still being debated. Signals generated through TCR upon interaction with self MHC-peptide complexes are critical for maturation of the CD4+ helper and CD8+ cytotoxic subsets. We have observed maturation of CD4+ but not CD8+ T cells in Ly-6A.2 transgenic MHC null mice. Since there can be no interactions with MHC molecules in these mice, these CD4+ cells must express the T cell repertoire that exists before positive and negative selection. Interestingly, despite an absence of selection by MHC molecules, the CD4+ cells that mature recognize MHC molecules at a frequency as high as in CD4+ cells in normal mice. These results demonstrate that: 1) the germline sequences encoding TCRs are biased toward reactivity to MHC molecules; and 2) CD4+ cells as opposed to CD8+ cells have distinct lineage commitment signals. These results also suggest that signals originating from Ly-6 can promote or substitute for signals generated from TCR that are required for positive selection. Moreover, this animal model offers a system to study T cell development in the thymus that can provide insights into mechanisms of lineage commitment in developing T cells.

Animals↗
PubMed1998

B-lymphocyte suppression in multiple myeloma is a reversible phenomenon specific to normal B-cell progenitors and plasma cell precursors.

The reduced levels of normal immunoglobulin in patients with myeloma may be due to suppression of normal B-cell differentiation. However, reports on the numbers of B cells vary, with some finding decreases consistent with immunoparesis, and others reporting expansions of phenotypically aberrant cells. We have therefore assessed the phenotype and levels of B lymphocytes in patients at presentation (n = 23), in plateau or complete remission (PB n = 42, BM n = 18), and in relapse (PB n = 17, BM n = 14), in comparison to normal individuals (n = 10). Phenotypic analysis was performed using five-parameter flow cytometry, with CD14 used to exclude monocytes where necessary. We found no evidence of a phenotypically distinctive blood or marrow B-cell population in patients with myeloma, nor of an increase in the levels of any B-cell subset. Numbers of blood CD19+ 38+ normal plasma cell precursors were significantly reduced in presentation/relapse patients, but not in patients in plateau/remission. Total CD19+ cells were significantly reduced only in patients with circulating myeloma cells, detected by IgH-PCR. In the marrow, CD19+ B cells expressing CD5, CD10, CD34, CD38, CD45(low) and Syndecan-1 were significantly decreased at presentation/relapse, but not in patients in plateau/remission. The majority of these antigens are expressed by normal B-cell progenitors, indicating that myeloma also affects the early stages of B-cell development. The suppression of progenitor cells was not restricted to B-lymphoid differentiation, as total CD34+ cells were also significantly reduced in the marrow of myeloma patients at presentation. These results indicate that, if neoplastic B cells are present in myeloma, they are low in number and have a phenotype similar to their normal counterparts. Furthermore, there is a reversible suppression of CD19+ B lymphocytes that correlates inversely with disease stage, and specifically affects the early and late stages of normal B-cell differentiation.

Adult↗
PubMed1997

Changing Health Care Environments and Adolescent Health Care: Legal and Policy Challenges.

The changes in the health care system and shifts toward managed care affect adolescents like all other age groups. This chapter deals with the key issues that concern adolescent health care providers while creating the health care models of the future. Questions such as adequate health insurance for adolescents, health care delivery to uninsured and underinsured adolescents, and protection of confidentiality all need to be addressed for adolescents to receive the health care they need.

Journal Article↗
PubMed1996

School-Based Primary Care in a Managed Care Environment: Options and Issues.

As school-based health centers have established a track record in providing access to primary care services for underserved school-age populations, financial viability of these programs has become increasingly dependent upon revenues generated from Medicaid and other third-party payers. The introduction of managed care concepts into this situation has created great uncertainty for the future. The authors discuss the various types of managed care models that school-based health centers are being called upon to work with and summarize the key issues (communications, confidentiality, linkages, reimbursement, and quality improvement) around which those relationships are being developed.

Journal Article↗