Search PubMed⌕ Search

Biomedical subjects

A Singer

Publications and source records attributed to A Singer.

428 records · Page 24Linked to original sources
PubMedDate not supplied

T-cell recognition of a chimaeric class II/class I MHC molecule and the role of L3T4.

In addition to expressing clonally distributed antigen-specific and major histocompatibility complex (MHC)-restricted receptors, T cells also express non-clonally distributed surface molecules that are involved in T-cell function. Among the most intriguing of the latter are L3T4 and Lyt 2, which are expressed on individual T lymphocytes in striking, though not absolute, concordance with their restriction by either class II or class I MHC determinants, and which are thought to contribute to the overall avidity of T-cell interactions by binding to monomorphic determinants on class II and class I MHC molecules, respectively. To examine the ability of T cells to recognize a single class II domain in the absence of the remainder of the Ia molecule, as well as to evaluate the structural basis for the putative interaction of L3T4 with Ia, a recombinant class II/class I murine MHC gene was constructed and introduced into mouse L cells. Here we demonstrate that a subset of class II allospecific cytotoxic T lymphocytes (CTL) can specifically recognize and lyse L-cell transfectants expressing an isolated polymorphic A beta 1 domain, and that anti-L3T4 antibody can block such killing, a result inconsistent with the highly conserved membrane-proximal domains of Ia acting as unique target sites for L3T4 binding.

Animals↗
PubMedDate not supplied

Analysis of T-cell subsets in rejection of Kb mutant skin allografts differing at class I MHC.

The T-cell subpopulations which initiate and mediate tissue allograft rejection remain controversial. In the present study we attempted to identify the phenotype and function of the T-cell subset(s) primarily responsible for the rejection of skin allografts differing at a single class I locus in the major histocompatibility complex (MHC). We found that the rejection rates by B6 mice (H-2b) of four different class I mutant (Kbm) skin allografts form a distinct hierarchy. This hierarchy correlates strikingly and uniquely with the relative precursor frequencies of Lyt2+ interleukin-2-secreting T-helper cells reactive against the various Kbm mutants. To investigate the role of Lyt2+ T cells in the rejection of class I-disparate skin allografts directly, H-2b nude mice were engrafted with Kbm skin allografts and then reconstituted with L3T4+ or Lyt2+ T-cell subpopulations from syngeneic H-2b mice. Lyt2+ T cells were observed to be both necessary and sufficient for the rejection of class I-disparate Kbm skin allografts, whereas L3T4+ T cells were neither necessary nor sufficient. These results identify the Lyt2+ interleukin-2-secreting T-cell subset as the critical cell type determining the rejection rate of class I-disparate Kbm skin allografts.

Animals↗
PubMedDate not supplied

Detection of cervical neoplasia using measurement of Brn-3a in cervical smears with persistent minor abnormality.

Measurement of the Brn-3a cellular transcription factor in cervical smears from women referred for colposcopy may improve the detection of underlying cervical neoplasia. In those women referred with persisting borderline or mildly dyskaryotic smears, those who had histologically proven underlying CIN II/III, had statistically significant higher Brn-3a levels than those with a similar smear but histologically shown to have HPV, CIN I, or no cervical abnormality. These results indicate that Brn-3a could play an important role in the near future in improving cervical cancer screening.

Adult↗
PubMedDate not supplied

A real time optoelectronic device as an adjunct to the Pap smear for cervical screening: a multicenter evaluation.

We report on the results from a multicenter trial for a real time optoelectronic device as an adjunct to the Pap smear for cervical screening. TruScreen (Polartechnics Limited, Sydney, Australia) is an automated device which measures the response to optical and electrical stimulation of the cervix and returns a screening result in real time. Analysis was performed on a group of 651 subjects recruited at 10 centers. Cytology and histology analyses were performed by centralized laboratories, with the cytology classification performed according to the Bethesda 2001 system. The sensitivities for histologically confirmed CIN 2/3 lesions by TruScreen, Pap, and TruScreen/Pap combined were 70% (95% CI: 67-74), 69% (CI: 65-72), and 93% (CI: 91-95), respectively. For histologically reported CIN 1, the sensitivities of the TruScreen, Pap, and combined test were 67% (CI: 63-70), 45% (CI: 41-49), and 87% (CI: 84-89). The improvement in sensitivity for the combined test compared to the Pap smear alone was significant (P = 0.002). Because TruScreen and cytology detect partly different but overlapping groups of CIN cases, the adjunctive combination provides very high CIN detection rates.

Adult↗
PubMedDate not supplied

Accuracy of implant impression splinted techniques: effect of splinting material.

Three implant impression techniques, using 3 different splinting materials, were assessed for accuracy in a laboratory model that simulated clinical practice. For group A, an autopolymerizing acrylic resin was used to splint transfer copings. In group B, a dual-cure acrylic resin was used, and for group C, plaster, which was also the impression material, was used. A metal implant master cast with an implant master framework was made to accurately fit to the cast. This cast was the standard for all impressions. For each group, 15 impressions were made. Polyether impression material was used for groups A and B. The accuracy of the stone casts with the implant analogues was measured against the master framework, using strain gauges. A multiple analysis of variance with repeated measures was performed to test for significant differences among the 3 groups. Additional analyses of variance were carried out to locate the source of difference. The statistical analyses revealed that a significant difference existed between groups A and B and between groups B and C but not between groups A and C. Impression techniques using autopolymerizing acrylic resin or impression plaster as a splinting material were significantly more accurate than dual-cure acrylic resin. Plaster is the material of choice in completely edentulous patients, since it is much easier to manipulate, less time consuming, and less expensive.

Acrylic Resins↗
PubMedDate not supplied

Cervical smears following laser treatment. Comparison of Cervex brush versus Cytobrush-Ayre spatula sampling.

For 802 women at initial follow-up after laser treatment of cervical lesions, 421 smears prepared using the Cervex brush were compared with 381 smears prepared using the combination of a Cytobrush plus an Ayre spatula. The smears were graded for adequacy, the presence of endocervical or metaplastic cells and the presence and degree of epithelial abnormalities. Endocervical or metaplastic cells were seen more often in Cytobrush-Ayre spatula smears (94.5%) as compared with Cervex brush smears (88.8%; P = .004). Also, the number of samples classed as inadequate was significantly greater with Cervex brush smears (4.0%) than with Cytobrush-Ayre spatula smears (0.3%; P = .0003). The number of smears showing dysplasia was too small to detect realistic differences between the two sampling methods. These findings suggest that, in women who have had laser treatment of the cervix, Cytobrush plus Ayre spatula sampling produces better-quality smears than does Cervex brush sampling, with regard to both adequacy and the presence of endocervical cells.

Adult↗
PubMedDate not supplied

Cement-retained implant-supported fixed partial dentures: a 6-month to 3-year follow-up.

This study presents a follow-up of 92 implant-supported fixed partial dentures that have been cement retained for 6 months up to 3 years. Included in the study were 41 women and 29 men. A total of 225 implants were placed (86 in the maxilla and 139 in the mandible). Fixed partial dentures, including single-tooth restorations, were temporarily cemented using Temp-Bond or IRM. Complications encountered were cement washout, procelain fracture, loose central screws, and implant failure. This study suggests an alternative to screw-retained prostheses; the method presented may lower the reported complications.

Adult↗