Parsimony in evolution, a natural fact

In a model, alternative pathways of molecular evolution are described, which exceed the usual evolutionary rate of phylogenetic binary trees, especially in the case of neutral mutations.     

Intraspinal synovial cysts: MR imaging

Juxtaarticular intraspinal synovial cysts are unusual lesions of the spine associated with facet arthropathy. These lesions can cause radicular symptoms and may masquerade clinically as other, more common entities. Synovial cysts have been detected at myelography and have been well characterized at computed tomography as posterolateral epidural masses, typically at L4-5. Six synovial cysts of the lumbar spine were demonstrated on magnetic resonance (MR) images. The signal-intensity patterns of these lesions are variable. MR imaging can be used to document the presence of hemorrhage within the cyst, which may relate to the exacerbation of symptoms. Air-filled synovial cysts may be difficult to detect and distinguish from facet arthropathy.     

Young people's alcohol consumption in public drinking places: reasoned behaviour or related to the situation?

Two contrasting perspectives are used to study correlates of young people's (16–25 years) alcohol consumption in public drinking places. One perspective is the theory of reasoned behaviour, or the Fishbein-Ajzen model, extended with self-efficacy. The other perspective assumes that exposure to drinking situations and aspects of the actual drinking situation (size of drinking group and group pressure) determine young people's alcohol consumption. Multiple regression analysis shows that variables indicating situational influences are correlated with the alcohol consumption of young men and women, even when controlling for the Fishbein-Ajzen variables. Among young men frequency of visiting public drinking places contributes more to the explained variance than the four Fishbein-Ajzen variables together. Young people's alcohol consumption in public drinking places appears to be less fully controlled by alcohol-specific beliefs, norms and perceived skills than the Fishbein-Ajzen model assumes. The Fishbein-Ajzen variables are only weakly correlated with the variables indicating situational influences. It is concluded that, from the individual's perspective, the influence of situational factors means that pan of his consumption is determined by more or less accidental circumstances like the opportunities to drink, the size of the drinking group and group pressure.     

Spontaneous infection of soft tissue haematomas in two HIV seropositive haemophilia patients

Two HIV seropostiive haemophilic patients with spontaneous infected soft tissue haematomas are described. In one patient the prepatellar bursa was infected, and in the other the posterior aspect of the shoulder. Treatmetn included evacuation of the suppurative focus, antibiotic therapy and prompt rehabilitation. The results were good in both cases and therefore operative management is recommended.     

Nasal T-cell lymphoma: a clinicopathological and immunophenotypic analysis of 13 cases

Thirteen cases of nasal lymphomas with T-cell or natural killer (NK)-cell phenotype were studied, with attention to clinical presentation and follow-up, the presence of Epstein-Barr virus (EBV) using in situ hybridization (EBER), the immunophenotype, and the presence of cytotoxic granules. All but two patients presented with stage I disease. In three cases local progression resulted in involvement of the central nervous system. When dissemination occurred, this was predominantly to extranodal localizations, in two cases to the skin. Response to therapy was highly variable, but patients treated with radiotherapy with or without additional chemotherapy had a better prognosis than patients treated with initial chemotherapy alone. All lymphomas were associated with EBV, and most cases howed cytotoxic features, ten of which were CD56 positive. In eight cases a T-cell origin was proven, but in five ases a possible NK-cell origin could not be excluded, No clinical differences were seen between true T-cell lymphomas and possible NK-cell neoplasms. Nasal T-cell lymphomas should be considered as a distinct clinicopathological entity, strongly associated with EBV, and with cytotoxic features in most cases. No prognostic parameters were detected to predict dissemination and response to therapy.     

Identification of human juvenile chronic myelogenous leukemia stem cells capable of initiating the disease in primary and secondary SCID mice

Most juvenile chronic myelogenous leukemia (JCML) cells have limited long-term proliferative capacity, and only a minority of immature cells give rise to colonies in semisolid cultures. Clonogenic JCML progenitors cannot be maintained in culture because they differentiate, and within a few weeks the leukemic clone is lost. This makes it difficult to identify the cell that initiates and maintains the disease in patients. To determine the proliferative capacity of JCML cells in vivo, bone marrow (BM), peripheral blood, or spleen cells from eight patients with JCML either at diagnosis or during treatment were transplanted into sublethally irradiated severe combined immune deficient (SCID) mice. JCML cells from all patients homed to the murine BM and proliferated extensively in response to exogenous stimulation with granulocyte-macrophage colony-stimulating factor. Within a few weeks, highly engrafted mice became ill and cachectic due to infiltration of leukemic cells and secretion of tumor necrosis factor- alpha. Murine BM, spleen, and liver were infiltrated with leukemic blasts, and typical JCML colony-forming progenitors could be recovered. Kinetic experiments demonstrated that only a small minority of transplanted cells homed to the murine BM, and that these cells initiated and maintained the disease in vivo by extensive proliferation and differentiation. To characterize the cell-surface phenotype of the JCML initiating cell (JCML-IC), JCML blood or spleen cells were fractionated on the basis of CD34/CD38 marker expression and transplanted into SCID mice. Only immature CD34+ cells could initiate the disease, while mature CD34- cells did not engraft. Within the CD34+ compartment, there was enrichment for JCML-ICs by immature cells with a CD34+/CD38- stem-cell-like phenotype. Mice transplanted with more mature CD34+/CD38+ populations that also contained clonogenic JCML progenitors were poorly engrafted. These results indicate that the JCML- IC is an earlier stage of development than clonogenic JCML progenitors. Additional evidence that the JCML-IC has stem-cell properties comes from secondary transplant experiments that test the self-renewal capacity. The JCML-IC from all three patients tested could successfully reinitiate the disease in secondary murine recipients. Thus, we have developed a functional in vivo model that replicates many aspects of human JCML, and have used this model to identify and characterize JCML- ICs and their stem-cell properties.     

EFFECT OF TOPICAL TRETINOIN ON EPIDERMAL LANGERHANS'CELLS IN PHOTODAMAGED SKIN

Background. Topical tretinoin has been successfully applied to treat photoaging; however, a decrease in the number of Langerhans’cells (LC) has been reported after its topical application in Macaque skin. A study was performed to evaluate the possible effect of topical tretinoin on the number of LC in human beings. Methods. Eight patients were studied. Topical tretinoin was applied in progressively increasing concentrations: 0.025% for 1 month, 0.05% for one month and 0.1% for 4 months. A skin biopsy from the malar area was taken before this therapy and 6 months later. To study LC, 4 p frozen sections were stained with the anti-CD1 antibody. Results. The number of CD1+ cells did not change when they were counted per unit of epidermal length, but they decreased when they were counted per unit of epidermal surface. Conclusions. These results indicate that topical tretinoin might damage epidermal Langerhans’cells, when it is applied for long periods of time; future studies are necessary to clarify this point.