A principal components analysis self-organizing map.

We propose a new self-organizing neural model that performs principal components analysis. It is also related to the adaptive subspace self-organizing map (ASSOM) network, but its training equations are simpler. Experimental results are reported, which show that the new model has better performance than the ASSOM network.     

Basal B-cell receptor signaling in B lymphocytes: mechanisms of regulation and role in positive selection, differentiation, and peripheral survival

Summary:  B-cell development is a highly ordered multistep process dependent upon signals generated by the pre-B and B-cell antigen receptor (BCR). BCR signals drive maturation of the B cell by integrating a number of parallel and sequential biological processes that result in generation of fully immunocompetent B cells. Among these biological processes are positive selection through several developmental checkpoints, negative selection of potentially self-reactive B cells, and activation of the mature B cell. In addition, recent studies have shown that developing and mature B cells rely on the constant activity of the BCR for their continued survival. Ligand (antigen)-dependent and -independent mechanisms of BCR signaling have been proposed, but their specific contributions to B-cell maturation and differentiation in the bone marrow and periphery are not completely clear. We discuss here a model, whereby ligand-independent basal BCR activity would be sufficient to trigger B-cell development through to the mature stage. However, long-term survival and formation of specific mature B-cell populations may be dependent on ligand–receptor interactions.     

Prospective clinical outcomes of revision fusion surgery in patients with pseudarthrosis after posterior lumbar interbody fusions using stand-alone metallic cages.

BACKGROUND CONTEXT: Posterior lumbar interbody fusion (PLIF) is a popular method of arthrodesis for surgical treatment of instabilities and degenerative conditions of the spine. With the introduction of threaded titanium cage devices, surgeons began performing PLIF procedures using these cages as stand-alone devices. Complications have been reported, however, including pseudarthrosis with persistent pain. Outcomes after revision surgical treatment for these patients with failed PLIF are not known. PURPOSE: To prospectively evaluate clinical outcomes of revision fusion surgery in patients who previously underwent posterior lumbar interbody fusion with stand-alone metallic cages resulting in pseudarthrosis. STUDY DESIGN/SETTING: Prospective case series. METHODS: Nineteen patients referred to the senior author were evaluated and diagnosed with pseudoarthrosis having previously undergone a PLIF procedure with stand-alone metallic cages. History, physical exam, and imaging studies were performed preoperatively and postoperatively. All underwent revision posterolateral fusion with iliac crest graft and pedicle screw instrumentation. Patient demographics, SF-36, and Oswestry Disability Index (ODI) data were collected prior to surgery and two years postoperatively. RESULTS: Patients undergoing revision fusion surgery were found to have had extensive facetectomies and pseudarthrosis intraoperatively. Outcomes data was collected on eighteen of nineteen patients (95%). Mean clinical follow up was 3.2 years (range 2.5-3.5 years). Seventeen patients (94%) achieved a solid fusion. Improvement was noted in seven of eight SF-36 sub-categories, but was significant only in two (Physical Function and Role Emotional). There was no significant difference in ODI scores. CONCLUSIONS: Pseudarthrosis should be considered in the differential diagnosis if severe symptoms persist in patients who undergo PLIF with stand-alone metallic cages. Successful revision fusion did not always correlate with improved clinical outcomes in these challenging patients undergoing further surgery. Performing PLIF using stand-alone metallic cages, especially after total resection of the facet joints, is not advocated unless supplemental instrumentation is utilized.     

Immunity in HIV-1-Infected Adults with a Previous State of Moderate-Severe Immune-Suppression and More Than 500 CD4+ T Cell After Highly Active Antiretroviral Therapy

We evaluated phenotypic and functional parameters of immune restoration of 27 HIV-infected patients on highly active antiretroviral therapy (HAART) (HIV-cases) with HIV-RNA levels below detectable limits at least during 18 months, and CD4+ cell per microliter higher than 500 at the moment of the study and lower than 300 anytime before. These patients were compared with 11 HIV-controls that never had less than 500 CD4+ cell per microliter and 20 healthy-controls (HIV seronegative subjects) in a cross-sectional study. HIV-cases had lower counts of naïve CD4+ than HIV-controls and healthy-controls. HIV-patients (both HIV-cases and HIV-controls) showed higher values of naïve and memory CD8+ counts than healthy-controls. TREC-bearing cell levels were significantly lower in HIV-cases than in healthy-controls. Peripheral blood mononuclear cells (PBMC) cultures, HIV-cases had lower values in proliferation to streptokinase (SK) and tetanus toxin (TT) than in healthy-controls. HIV-cases had lower IFN-γ and higher IL-5 production with pokeweed than healthy-controls (P < 0.01). However, IL-5 production of HIV-cases after TT stimulation was lower than in HIV-controls and healthy-controls. Total IgG and IgG1 levels were significantly higher in HIV-cases than in HIV-controls and healthy-controls. Also, IgM levels were significantly higher in HIV-cases than in healthy-controls. Nevertheless, IgG2 levels were significantly lower in HIV-cases and HIV-controls than in healthy-controls. The levels of specific Igs antipneumococcal capsular polysaccharide and TT were significantly lower in HIV-cases than in healthy-controls. HIV-patients with a previous state of severe-moderate immunosuppression normalizing their CD4+ counts have a incomplete immune reconstitution after HAART. Long-term consequences of this subclinical immune deficiency remain to be determined.     

Molecular cytogenetic characterization of a complex rearrangement involving chromosomes 9 and 22 in a case of Ph-negative chronic myeloid leukemia

The "golden path", produced by the Human Genome Project effort, is composed of a collection of overlapping and fully sequenced BAC/PAC clones covering almost completely the human genome. These clones can be advantageously exploited as fluorescence in situ hybridization (FISH) probes for the characterization of rearrangements frequently found in tumors. Breakpoint characterization can be further refined by generating additional smaller FISH probes through LONG-PCR amplification of specific DNA segments, 5-10 kb in size, using appropriate BAC/PAC probes as template. We report here an example of this approach that has been used to characterize a complex Ph-negative chronic myeloid leukemia (CML Ph-) case in which the BCR/ABL fusion gene was found located on chromosome 9.     

Risk factors for urinary incontinence in women

OBJECTIVES: To review the epidemiological evidence on risk factors for urinary incontinence (UI) in women. METHODS: Using Medline and a manual search we identified the main papers published in English up to 1998. RESULTS: There is consistent evidence that the frequency of UI increases with age, but there is little information on the frequency of different types of UI in different age groups. With regard to other risk factors, there is a clinical consensus that vaginal delivery and, more in general, obstetric traumas are associated with UI, although epidemiological studies are not always consistent. Less defined is the role of race, menopausal status, history of gynecological surgery, body mass index, smoking, and coffee and alcohol consumption on the risk of UI. CONCLUSION: In the coming years, epidemiological research should focus particularly on the potential differences in the epidemiological characteristics of different types of UI in order to gain insight into the pathogenic mechanisms.     

The surgical treatment of fractures of the proximal end of the tibia: a review of cases as related to prognostic factors

It is the purpose of this retrospective study to analyze factors capable of influencing clinical-functional and radiographic results, such as type of fracture, age of the patients, type of trauma, delay in treatment, associated lesions. A total of 33 fractures treated by open reduction and internal stabilization for fractures of the proximal tibia classified according to the AO were re-evaluated. Clinical and radiographic evaluation were obtained by assessing arthrosis, axis, and sinking of the tibial plateau. The clinical and functional results were satisfactory in 72.2% of cases, and radiographic ones were satisfactory in 63.6% for gonarthrosis, in 81.6% for axis, and in 84.8% for sinking. In conclusion, factors capable of influencing the results, such as type of fracture, age of the patient, and type of trauma, in addition to variables that the surgeon must monitor, such as reconstruction of the joint, alignment, synthesis, treatment of meniscal lesions, were observed.     

Mode of Childbirth in Low-Risk Pregnancies: Nicaraguan Physicians’ Viewpoints

To explore attitudes of physicians attending births in the public and private sectors and at the managerial level toward cesarean birth in Nicaragua. A qualitative study was conducted consisting of four focus groups with 17 physicians and nine in-depth interviews with decision-makers. Although study participants listed many advantages of vaginal birth and disadvantages of cesarean birth, they perceived that the increase in the cesarean birth rate in Nicaragua has resulted in a reduction in perinatal morbidity and mortality. They ascribed high cesarean birth rates to a web of interrelated provider, patient, and health system factors. They identified five actions that would facilitate a reduction in the number of unnecessary cesarean operations: establishing standards and protocols; preparing women and their families for labor and childbirth; incorporating cesarean birth rate monitoring and audit systems into quality assurance activities at the facility level; strengthening the movement to humanize birth; and promoting community-based interventions to educate women and families about the benefits of vaginal birth. Study participants believe that by performing cesarean operations they are providing the best quality of care feasible within their context. They do not perceive problems with their current practice. The identified causes of unnecessary cesarean operations in Nicaragua are multifactorial, so it appears that a multi-layered strategy is needed to safely reduce cesarean birth rates. The recent Nicaraguan Ministry of Health guidance to promote parto humanizado (“humanization of childbirth”) could serve as the basis for a collaborative effort among health care professionals, government, and consumer advocates to reduce the number of unnecessary cesarean births in Nicaragua.