Injection-compression sclerotherapy.
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Female↗
Biomedical subjects
A Singer
Publications and source records attributed to A Singer.
Can physics and physical chemistry explain the workings of homeopathy? A clinician's view.
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Australia↗
The Polarprobe--emerging technology for cervical cancer screening.
The Polarprobe is a portable non invasive electronic device designed for the detection of cervical precancer and cancer. It measures both electrical and optical properties of cervical tissue to allow a real time comparison with a databank of previously determined cervical tissue types. The need for additional tests to augment or even replace the Papanicolaou smear has partly prompted its development. Indeed it has been shown to be associated with less pain and anxiety than the smear and has the capability of encouraging women to attend for screening. Some of the preliminary clinical trials on the Polarprobe are reported as well as the ongoing developments and modifications to the device.
Electrodiagnosis↗
T cell receptor (TCR)-induced death of immature CD4+CD8+ thymocytes by two distinct mechanisms differing in their requirement for CD28 costimulation: implications for negative selection in the thymus.
Negative selection is the process by which the developing lymphocyte receptor repertoire rids itself of autoreactive specificities. One mechanism of negative selection in developing T cells is the induction of apoptosis in immature CD4+CD8+ (DP) thymocytes, referred to as clonal deletion. Clonal deletion is necessarily T cell receptor (TCR) specific, but TCR signals alone are not lethal to purified DP thymocytes. Here, we identify two distinct mechanisms by which TCR-specific death of DP thymocytes can be induced. One mechanism requires simultaneous TCR and costimulatory signals initiated by CD28. The other mechanism is initiated by TCR signals in the absence of simultaneous costimulatory signals and is mediated by subsequent interaction with antigen-presenting cells. We propose that these mechanisms represent two distinct clonal deletion strategies that are differentially implemented during development depending on whether immature thymocytes encounter antigen in the thymic cortex or thymic medulla.
Animals↗
Limiting dilution analysis of primary cytotoxic T-cell precursors.
An efficient colorimetric assay has been adapted for limiting dilution analysis of cytotoxic T-cell precursors. Application of this assay in a suitable experimental model of thymic education could be especially useful in identifying factors that shape the CD8 T-cell repertoire. The essential elements of such a model are described here and elsewhere.
Animals↗
Commitment of immature CD4+8+ thymocytes to the CD4 lineage requires CD3 signaling but does not require expression of clonotypic T cell receptor (TCR) chains.
As a consequence of positive selection in the thymus, immature CD4(+)8(+) double-positive, [DP] thymocytes selectively terminate synthesis of one coreceptor molecule and, as a result, differentiate into either CD4(+) or CD8(+) T cells. The decision by individual DP thymocytes to terminate synthesis of one or the other coreceptor molecule is referred to as lineage commitment. Previously, we reported that the intrathymic signals that induced commitment to the CD4 versus CD8 T cell lineages were markedly asymmetric. Notably, CD8 commitment appeared to require lineage-specific signals, whereas CD4 commitment appeared to occur in the absence of lineage-specific signals by default. Consequently, it was unclear whether CD4 commitment, as revealed by selective termination of CD8 coreceptor synthesis, occurred in all DP thymocytes, or whether CD4 commitment occurred only in T cell receptor (TCR)-CD3-signaled DP thymocytes. Here, we report that selective termination of CD8 coreceptor synthesis does not occur in DP thymocytes spontaneously. Rather, CD4 commitment in DP thymocytes requires signals transduced by either CD3 or zeta chains, which can signal CD4 commitment even in the absence of clonotypic TCR chains.
Animals↗
Incomplete endoplasmic reticulum (ER) retention in immature thymocytes as revealed by surface expression of "ER-resident" molecular chaperones.
The folding and assembly of nascent proteins in the endoplasmic reticulum (ER) is assisted by molecular chaperones that are themselves retained within the ER. We now report that a number of different ER proteins, including molecular chaperones, are selectively expressed on the surface of immature thymocytes, but their surface expression is extinguished upon further differentiation. Escape from the ER is only possible for newly synthesized ER proteins before they become permanently retained. Thus, the cellular process of ER retention is incomplete in immature thymocytes and provides an explanation for surface expression of partial receptor complexes that transduce differentiative signals during thymic development.
Blotting, Western↗
Surface molecules that drive T cell development in vitro in the absence of thymic epithelium and in the absence of lineage-specific signals.
Differentiation of immature double positive (DP) CD4+ CD8+ thymocytes into single positive (SP) CD4+ and CD8+ T cells is referred to as positive selection and requires physical contact with thymic cortical epithelium. We now have identified "coinducer" molecules on DP thymocytes that, together with TCR, signal DP thymocytes to differentiate into SP T cells in vitro in the absence of thymic epithelium. A remarkable number of different molecules on DP thymocytes possessed "coinducing" activity, including CD2, CD5, CD24, CD28, CD49d, CD81, and TSA-1. Interestingly, in vitro differentiation occurred in the absence of lineage-specific signals, yet resulted in the selective generation of CD4+CD8- T cells. Thus, the present study has identified surface molecules that can signal DP thymocytes to differentiate into SP T cells in the absence of thymic epithelium and has characterized a default pathway for CD4+ T cell differentiation.
Animals↗
A spontaneously arising mutation in the DLAARN motif of murine ZAP-70 abrogates kinase activity and arrests thymocyte development.
Development of immature CD4+ CD8+ thymocytes into functionally mature CD4+ and CD8+ T cells is driven by selection events that require signals transduced through the T cell antigen receptor (TCR). Transduction of TCR signals in the thymus involves tyrosine phosphorylation of the protein tyrosine kinase ZAP-70 by p56(lck) and results in induction of ZAP-70 enzymatic activity. We have identified a novel, spontaneously arising point mutation within a highly conserved motif (DLAARN) in the kinase domain of murine ZAP-70 that uncouples tyrosine phosphorylation of ZAP-70 from induction of ZAP-70 kinase activity. Mice homozygous for this mutation are devoid of mature T cells because thymocyte development is arrested at the CD4+ CD8+ stage of differentiation. The developmental arrest is due to the inability of CD4+ CD8+ thymocytes to propagate TCR signals in the absence of ZAP-70 kinase activity despite tyrosine phosphorylation of TCR-associated ZAP-70 molecules.
Amino Acid Sequence↗
NMR structure of neuromedin C, a neurotransmitter with an amino terminal CuII-, NiII-binding (ATCUN) motif.
The structure of neuromedin C, a 10-residue bombesin-like neuropeptide with the sequence Gly-Asn-His-Trp-Ala-Val-Gly-His-Leu-Met-NH2, has been investigated. Like human serum albumin, neuromedin C contains the amino-terminal CuII-, NiII-binding (ATCUN) motif which has high affinity for CuII and NiII. The solution structure of the NiII-peptide complex has been calculated based on 2D ROESY data obtained at 25 degrees C, using a hybrid distance geometry-simulated annealing approach. Comparison of 1H, 13C and 15N chemical shifts and ROESY data in the presence and absence of NiII demonstrates that the metal binds at the N-terminus of the peptide, leading to a conformational change. The metal complex adopts a conformation comprising two connected turns including residues 1Gly to 3His and 5Ala to 8His. The first turn corresponds to the NiII coordination ligands in a square planar conformation, and the second reflects the interaction between 4Trp and 8His. The results may have important physiological implications in the phenomenon of neurotransmission.
Amino Acid Sequence↗
Protective effect of depot-medroxyprogesterone acetate on surgically treated uterine leiomyomas: a multicentre case-control study.
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Antineoplastic Agents, Hormonal↗
Cathepsin E expression by normal and premalignant cervical epithelium.
We have investigated the expression of the aspartic proteinase cathepsin E and HLA-DR and the presence of HPV16 in normal squamous epithelium (n = 8) and low-grade (n = 21) and high-grade (n = 14) intraepithelial squamous lesions of the uterine cervix. Immunohistochemistry of cervical biopsies revealed that up-regulation of cathepsin E expression was related to increasing severity of the cervical intraepithelial neoplasia (CIN). Up-regulation of protein was associated with increased message as assessed by in situ hybridization. Langerhans cells and the majority of koilocytes did not express detectable cathepsin E levels. Although there was also an up-regulation of HLA-DR expression by cervical keratinocytes in cervical intraepithelial neoplasia lesions, as determined by immunohistochemistry, no significant correlation was found between HLA-DR and cathepsin E expression in these lesions; neither was expression of cathepsin E correlated to the presence of HPV16, detected by polymerase chain reaction. The expression of cathepsin E, an aspartic proteinase that is reported to play a role in antigen processing for presentation by class II major histocompatibility complex molecules, is associated with cellular dedifferentiation in cervical intraepithelial neoplasia.
Adolescent↗
Tuning of activation thresholds explains flexibility in the selection and development of T cells in the thymus.
Immature CD4+ CD8+ thymocytes expressing T-cell antigen receptors (TCR) are selected by TCR-mediated recognition of peptides associated with major histocompatibility complex molecules on thymic stromal cells. Selection ensures reactivity of the mature cells to foreign antigens and tolerance to self. Although much has been learned about the factors that determine whether a thymocyte with a given specificity will be positively or negatively selected, selection as an aspect of the developmental process as a whole is less well-understood. Here we invoke a model in which thymocytes tune their response characteristics individually and dynamically in the course of development. Cellular development and selection are driven by receptor-mediated metabolic perturbations. Perturbation is a measure of the net intracellular change induced by external stimulation. It results from the integration of several signals and countersignals over time and therefore depends on the environment and the maturation stage of the cell. Individual cell adaptation limits the range of perturbations. Such adaptation renders thymocytes less sensitive to the level of stimulation per se, but responsive to environmental changes in that level. This formulation begins to explain the mechanisms that link developmental and selection events to each other.
Animals↗
Lineage commitment in the thymus: only the most differentiated (TCRhibcl-2hi) subset of CD4+CD8+ thymocytes has selectively terminated CD4 or CD8 synthesis.
Lineage commitment is a developmental process by which individual CD4+CD8+ (double positive, DP) thymocytes make a decision to differentiate into either CD4+ or CD8+ T cells. However, the molecular event(s) that defines lineage commitment is controversial. We have previously proposed that lineage commitment in DP thymocytes can be molecularly defined as the selective termination of CD4 or CD8 coreceptor synthesis. The present study supports such a molecular definition by showing that termination of either CD4 or CD8 synthesis is a highly regulated event that is only evident within the most differentiated DP subset (CD5hiCD69hiTCRhibcl-2hi). In fact, essentially all cells within this DP subset actively synthesize only one coreceptor molecule. In addition, the present results identify three distinct sub-populations of DP thymocytes that define the developmental progression of the lineage commitment process and demonstrate that lineage commitment is coincident with upregulation of TCR and bcl-2. Thus, this study supports a molecular definition of lineage commitment and uniquely identifies TCRhibcl-2hi DP thymocytes as cells that are already committed to either the CD4 or CD8 T cell lineage.
Animals↗
Human papillomavirus genotype as a predictor of persistence and development of high-grade lesions in women with minor cervical abnormalities.
Women referred for colposcopy with mild and moderate dyskaryosis and found to have only minor cervical abnormalities were screened for oncogenic human papilloma virus (HPV) types. The natural development of these abnormalities in 42 HPV-positive women was assessed by cytology and colposcopy at 6-month intervals for up to 2 years. As is the case with cancers and high-grade cervical intra-epithelial neoplasia (CIN), minor cervical abnormalities were frequently found to be associated with HPV16, -18, -31 and -33. Viral persistence and the development of high-grade lesions were found to be closely associated with HPV16; 56% of HPV16 isolates were persistent compared to 7% of other HPV types, and all 4 subsequent CIN 3 lesions were in women with persistent infection. A striking association of persistence with a variant of HPV16 having a base change at nucleotide 350 was observed. Ten of 12 women with this variant had persistent infection compared to only 1 of 16 women infected with the HPV16 prototype.
Adult↗
Cognitive remediation of persons with severe and persistent mental illness.
There is a vast psychiatric literature describing the nature and degree of cognitive deficits present in persons suffering from severe and persistent mental illness, particularly schizophrenic spectrum disorders. A smaller, more recent literature has emerged addressing non-pharmaceutical interventions developed to remediate those deficits. The Cognitive Remediation Program was developed to remediate cognitive deficits in such areas as the ability to sustain attention and concentration, memory processes, concept formation, organizing visual and auditory stimuli into recognizable patterns, and shifting cognitive sets. The program consists of three fifteen minute intervals or "loops" that each contain a different type of task designed to promote remediation of cognitive deficits. The Program also employs behavioral techniques, using a token economy to aid in shaping behavior and motivating patients. The loops consist of: 1) a group that focuses on training in attention, concentration and cognitive flexibility; 2) a computer group utilizing a combination of game software and programs designed for use with a head injured population; 3) a group promoting the generalization of skills learned in the Program to other social arenas. On a ten week pre- and post-measure, participants improved significantly on both a digits forward and digits backward task, both measures of concentration and attention.
Adult↗
Risk factors for invasive cervix cancer in young women.
The aim of the study was to evaluate risk factors for invasive cervix cancer in young British women and to look for factors which might explain its increased incidence in younger ages. A case-control study involving 121 women with invasive cervix cancer diagnosed before the age of 40 years, and 241 matched controls was undertaken. Questions were asked about demography, sexual behaviour, reproductive and contraceptive history, smoking, diet and hygiene. Age at first intercourse and lifetime number of sexual partners were found to be the most important factors, whereas parity, educational attainment and social class were not related to risk. Smoking was only weakly related to risk (P = 0.01) and this effect disappeared after adjustment for sexual behaviour variables. A weak protective effective of increased fruit consumption was observed (P = 0.03), but again this became non-significant after adjustment for sexual behaviour. Only factors related to sexual behaviour were found to be important in this study and other cofactors often associated with invasive cancer in older women were not found to be involved. It is possible that genetic factors influencing viral persistence, and specific more virulent strains of human papillomavirus may be more important in early onset cases.
Adult↗
TCR activation of ZAP70 is impaired in CD4+CD8+ thymocytes as a consequence of intrathymic interactions that diminish available p56lck.
The fate of developing CD4+CD8+ thymocytes is determined by signals transduced through surface TCR complexes. Here, we report that cross-linking of TCR on CD4+ CD8+ thymocytes fails to activate ZAP70 protein tyrosine kinase and fails to initiate downstream signaling events, unless the TCR are coaggregated with surface coreceptor molecules. TCR signaling in CD4+CD8+ thymocytes is impaired because the number of available p56lck molecules is diminished by intrathymic CD4-Ia interactions that initially activate p56lck molecules, which are subsequently degraded. As a consequence of intrathymic CD4-Ia interactions, TCR zeta chains are initially phosphorylated to recruit ZAP70 molecules, but the recruited ZAP70 molecules are not subsequently phosphorylated, resulting in TCR complexes that are stably associated with inactive ZAP70 molecules. Thus, intrathymic interactions that diminish p56lck regulate TCR signaling thresholds and affect TCR structure in developing CD4+CD8+ thymocytes.
Animals↗