Fibrin as a cell carrier in cardiovascular tissue engineering applications

In cardiovascular tissue engineering approaches, efficient seeding methods are essential. To achieve this and to save time, cells can be encapsulated in gels. Combining the advantages of a gel as a cell carrier with the advantages of a fiber-based scaffold, providing structural integrity to the developing tissue, might offer several advantages. In this study, seeding by using fibrin as a cell carrier is compared to the conventional static seeding method with regard to tissue development. Seeding with fibrin resulted in less loss of soluble collagen into the medium and a more mature extracellular matrix in a shorter period of time. The use of fibrin degradation inhibitors was shown to inhibit extracellular matrix formation, although it did not hamper cell proliferation. The use of fibrin as a cell carrier to seed cells into a fiber-based scaffold may represent a promising, timesaving approach in cardiovascular tissue engineering applications.     

Microglia are more susceptible than macrophages to apoptosis in the central nervous system in experimental autoimmune encephalomyelitis through a mechanism not involving Fas (CD95)

Morphological studies have shown that macrophages and microglia undergo apoptosis in the central nervous system (CNS) in acute experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. To assess the relative levels of macrophage and microglial apoptosis, and the molecular mechanisms involved in this process, we used three-colour flow cytometry to identify CD45lowCD11b/c+ microglial cells and CD45highCD11b/c+ macrophages in the inflammatory cells isolated from the spinal cords of Lewis rats 13 days after immunization with myelin basic protein (MBP) and complete Freund's adjuvant. Simultaneously, we analyzed the DNA content of these cell populations to assess the proportions of cells undergoing apoptosis and in different stages of the cell cycle or examined their expression of three apoptosis- regulating proteins, i.e. Fas (CD95), Fas ligand (FasL) and Bcl-2. Microglia were highly vulnerable to apoptosis and were over-represented in the apoptotic population. Macrophages were less susceptible to apoptosis than microglia and underwent mitosis more frequently than microglia. The different susceptibilities of microglia and macrophages to apoptosis did not appear to be due to variations in Fas, FasL or Bcl- 2 expression, as the proportions of microglia and macrophages expressing these proteins were similar, and were relatively high. Furthermore, in contrast to T cell apoptosis, apoptosis of microglia/macrophages did not occur more frequently in cells expressing Fas or FasL, or less frequently in cells expressing Bcl-2. These results indicate that the apoptosis of microglia and CNS macrophages in EAE is not mediated through the Fas pathway, and that Bcl-2 expression does not protect them from apoptosis. Expression of FasL by macrophages and microglia may contribute to the pathogenesis and immunoregulation of EAE through interactions with Fas+ oligodendrocytes and Fas+ T cells. The high level of microglial apoptosis in EAE indicates that microglial apoptosis may be an important homeostatic mechanism for controlling the number of microglia in the CNS following microglial activation and proliferation.      

Seroepidemiological study on sexually transmitted diseases and hepatitis B in African promiscuous heterosexuals in relation to HTLV-III infection

A seroepidemiological study was performed on HTLV-III, T. pallidum, C. trachomatis and Hepatitis B virus (HBV), in Butare, Rwanda, among 33 female prostitutes, 25 male customers of prostitutes, and 60 male and female controls. As compared with female controls the prostitutes had a higher prevalence of antibodies to HTLV-III (29/33 versus 4/33, p<0.001), T. pallidunz (TPHA: 27/33 versus 6/33, p<0.001; RPR: 19/33 versus 233, p<0.001; FTA-Abs: 27/33 versus 5/33, p<0:001) and C. trachomatis (IgG IF: 31/33 versus 13/33, p<0.001). HBV serological markers were more often detected in the prostitutes than in the female controls (31/33 versus 18/33, p<0.001) although HBs antigen carriage rate was similar in both groups. As compared with male controls, the male customers of prostitutes had more frequently detectable antibodies to HTLV-III (7/25 versus 2/27, p = 0.05), and a positive RPR (10/25 versus 1/27, p<0.01). Among the 118 individuals studied, odds ratios and trend analysis disclosed a significant association between HTLV-III seropositivity and a positive TPHA, RPR, FTA-Abs, Chlamvdia IgG IF test and serological markers to HBV. No association was found between HTLV-III seropositivity and IIBs Ag carriage. This study suggests that HTLV-III has to be considered as an infectious agent transmitted among promiscuous Central African heterosexuals by sexual contact and/or parenteral contact with unsterile needles used for STD treatments.     

Factors Influencing the Growth in Knowledge of Trainees in General Practice

Objectives: The relation between the content of postgraduate training for general practice and the outcome in terms of the growth in knowledge of trainees was investigated. The training variables included were: (1) the number of patients seen per day, (2) the trainer, (3) the practice and (4) the theoretical curriculum.Methods: Subjects were 58 trainee-trainer pairs. Growth in knowledge was assessed by two written tests administered with eight months interval. Training variables were evaluated by means of questionnaires and logbook-registration. The correlation was explored between each of the training variables and the knowledge tests scores. To correct for interactional effects, a step-wise multiple regression analysis was performed with the second test as dependent variable and the first test as well as the training variables as independent variables.Results: Significant growth in knowledge was demonstrated. Non of all training variables investigated explained the variance in scores on the second test equally good or better than the scores on the entry test.Conclusions: The impact of the separate training-components on the growth in knowledge, remains unclear. We may speculate, that the sort of knowledge assessed with the written literature based true/false test is different from the sort of knowledge transferred during every day training: evidence based knowledge versus experience based knowledge. Equally valid is the conclusion that these findings fit into the theory that in adult learning the outcome is more learner than teacher dependent.This revised version was published online in September 2005 with corrections to the Cover Date.     

Stereotactic radiosurgery with adjusted linear accelerator for cerebral arteriovenous malformations: preliminary results in the Netherlands]

OBJECTIVE: To assess the effects of stereotactic radiosurgery of a cerebral arteriovenous malformation (AVM). DESIGN: Prospective. METHOD: In November 1991-December 1995 linear acceleration radiosurgery was performed on 29 patients for their 30 cerebral AVMs in the University Hospital Vrije Universiteit, Amsterdam, the Netherlands. There were 15 females and 14 males with a mean age of 37.1 years (range: 13-58). Generally one isocentre was used and 15 Gy was given to the margins of the AVM at the 80% isodose. The mean target volume was 2.4 ml (range; 0.5-8.2). After 6 months, one year and thereafter every year, neurological and MRI-controls took place, in the outpatient ward. Angiography was performed after an average of 35 months (range: 24-70) to check if the AVM had obliterated. RESULTS: Angiographic post-treatment results were available in 27 patients and MRI information in one. Angiographic obliteration occurred in 20 patients (71%). No permanent radiation-induced neurological deficit was seen, nor did any hemorrhage occur during the interval between irradiation and obliteration.     

How concordant are the estimated rates of natural conception and in-vitro fertilization/embryo transfer success?

Knowledge of the chance to conceive for the subfertile couple is important in the process of counselling and clinical decision making. There are no data available on the reproducibility of the clinician's ability to assess the chance to conceive, both after expectant management or treatment with in-vitro fertilization and embryo transfer (IVF-embryo transfer). We evaluated this reproducibility by means of a set of case histories presented to a panel of gynaecologists and endocrinologists. A poor reproducibility would indicate a strong need for the use of prognostic models. In 1995, 57 gynaecologists and 32 reproductive endocrinologists were asked to appraise the 1 year spontaneous conception chance as well as the cumulative success rate of three cycles for IVF-embryo transfer of four couples with different medical histories. The clinical and laboratory data of these couples were presented as case histories. The difference between the estimated spontaneous pregnancy chances and the success rate of IVF-embryo transfer was also calculated. Calculation of intra-class correlation coefficients, which can be considered as measures of the reproducibility, demonstrated a substantial reproducibility of the assessment of spontaneous conception chances, but a slight to fair reproducibility of the assessment of IVF-embryo transfer success rates. We conclude that the use of reliable prognostic models for IVF-embryo transfer in the management of subfertility is warranted.