Threshold concepts in dental education.

The paper presents a conceptual framework to inform dental education. Drawing from a vast body of research into student learning, the simple model presented here has an explanatory value in describing what is currently observed to happen and a predictive value in guiding future teaching practices. We introduce to dental education the application of threshold concepts that have a transformative role in offering a new vision of the curriculum that helps to move away from the medieval transmission model of higher education towards a dual processing model that better reflects the way in which professionals operate within the discipline. Threshold concepts give a role for the student voice in offering a novice perspective which is paradoxically something that is out of reach of the subject expert. Finally, the application of threshold concepts highlights some of the weaknesses in the competency-based training model of clinical teaching.

Effects of peptides cleaved from human fibrinogen by plasmin on rabbit kidney cells in culture.

Low molecular weight fibrinogen degradation products (LMW-FDP) containing a mixture of dialysable peptides cleaved from human fibrinogen by plasmin are cytotoxic to an established line of rabbit kidney cells and to primary cultures of rabbit kidney cells. The presence of LMW-FDP in a concentration of 50 micrograms/ml during the cell cultivation caused a considerable release of 51Cr from prelabelled cells and inhibited 3H-thymidine and 86Rb uptake. Among three isolated peptides of established primary structure only one, 6D: Ser-Gln-Leu-Gln-Lys-Val-Pro-Pro-Glu-Trp-Lys, induced a significant effect, i.e. it enhanced 3H-thymidine incorporation. Two others, 6A: Ala-Arg-Pro-Ala-Lys and 6E: Thr-Ser-Glu-Val-Lys, did not influence the examined parameters. Hence other components of LMW-FDP must be assumed to be responsible for the cytotoxic effect on kidney cell cultures.

Association of giant multinucleated cells with deterioration of osteoinductive potency of bone matrix.

A thirty four intramuscular implants of rat decalcified bone matrix into mice and rats were histologically inspected in order to find out if there is an inverse correlation between the induction of multinucleated giant cell formation and the bone induction activity. It was found that the presence of multinucleated giant cells which avidly resorbed the implanted matrix was almost always combined with the lack of local bone induction. In contrast, the specimens exhibiting intense bone induction were devoided of multinucleated giant cells. Our observation confirm the opinion expressed by Walters and Schneider that multinucleated giant cells induced by mineralized bone chips are not osteoclasts but a type of inflammatory cells, analogous if not identical to the "foreign body cells". It is postulated that formation of multinucleated giant cells is a morphological expression of hyperactivity of mononuclear phagocytes. Hyperactive multinucleated giant cells avidly resorb bone matrix and degrade bone inducing substance(s) like skeletal growth factor and/or bone morphogenetic peptides resulting in the deterioration or lack of bone induction.

Effect of interferon and poly I: C on DNA fiber propagation in L 929 cells.

Autoradiographic analysis of DNA fiber replication was used to measure the rate of DNA propagation, the distances between initiation points of adjacent replicons and the direction of DNA propagation in L929 cells treated with either interferon or poly I: C, or untreated. Poly I:C ceased by 44% the rate of DNA propagation while the interferon had no effect. Poly I:C but not interferon reduced the mean distance between initiation points by 32%.

Effect of poly I:C on cell proliferation in vivo.

Female Swiss albino mice were injected intraperitoneally with poly I:C1 microgram/g body weight. The animals were killed 2, 12, and 24 hr after the injection of poly I:C. Half an hour before the death of animals they were reinjected intraperitoneally with 3H-thymidine. Fragments of ileum were excised. The quantification of autoradiographs included the counting of labeled cells, mitotic cells as well as the recording of cell position along the ileal crypts. The spatial distribution of both the mitotic and DNA-synthesizing cells of colonic crypts were affected by poly I:C at neither of time intervals between the injection and the death of animals. On the other hand, the parameters of cellular proliferation, i.e. mitotic and labeling indices, decreased significantly 12 and 24 hr after the injection of poly I:C, being unaffected 2 hr after the injection.

Mast cells and basophils in murine lymph nodes stimulated by B-cell mitogen.

The total number of mast cells and basophilic granulocytes in lymph nodes activated in vivo by a B-cell mitogen (formaldehyde-fixed S. paratyphi B) remains unchanged in spite of a significant enlargement and cellularity of the lymph nodes. This is in contrast to the previous finding showing that T-cell mitogens reduce the number of granular cells in the lymph nodes.

Structural basis for antiviral activity of flavonoids-naturally occurring compounds.

The effect of different substituents of quercetin and luteolin on the ability to inhibit the herpes simplex virus (HSV-1) replication in RK-13 cells was studied. It seems that parent compounds with free hydroxyl groups at C-5, C-7, C-3', C-4' and additionally at C-3 have the highest activity. Substitution of those groups caused decrease of or completely abolished the antiviral activity of the tested compounds.

[Influence of newly synthesized sesquiterpenes--analogs of taxol on multiplication of herpes simplex virus (HSV-1MC) and retrovirus (Mo-MSV)]. / Wplyw nowo zsyntetyzowanych seskwiterpenowych analogów taksolu na namnazanie wirusa opryszczki (HSV-1 MC) oraz retrowirusa (Mo-MSV).

The study comprised newly synthesized sesquiterpenoid analogs of taxol. The synthesis of the compounds was performed at the Institute of Organic Chemistry, Polish Academy of Sciences. Cytotoxicity of the compound was assessed using formazan method. In in vitro studies the cell cultures were infected with HSV-1MC. The tested compounds were added in different concentrations to the cell culture after viral infection. Titer of the virus was expressed in TCID50/ml at particular stages of the experiments. In in vivo experiments NMRI mice were infected intramuscularly with a Moloney murine sarcoma virus (Mo-MSV). Tested compounds were administered to the mice intravenously on the day of virus inoculation. In Mo-MSV-infected mice dynamics of tumor progression and regression was assessed, as well as a mean time interval of tumor disappearance. Among the compounds tested: isovellerol-13-N-benzoyl-(2'R,3'S)-3'-phenylisoserinate, 5-deoxy-lactarolid B 8-[N-benzoyl-(2'R,3'S)-3'-phenylisoserinate] and isolactarorufin 8-epi-[N-benzoyl-(2'R,3'S)-3'-phenylisoserinate] showed significant antiviral activity in in vitro experiments. In in vivo experiments only lactarorufin A 8-[N-benzoyl-(2'R,3'S)-3'-phenylisoserinate] significantly inhibited the development of tumors and shortened the time of their total regression in the course of Mo-MSV infection.

[Contribution of fungi to chronic dermatitis and lymphangitis in patients with filariasis]. / Udzial grzybów w przewleklym zapaleniu skóry i naczyn limfatycznych u pacjentów z filarioza.

Adenolymphangitis is a common occurrence in filarial lymphedema. Damage to the lymphatics by F. bancrofti is followed by obliteration of lymph vessel and lymph stasis. Obstruction of lymphatics prevents the microbs skin penetration. Presented studies were performed to evaluate the role of fungi colonization of the skin among patients with filarial lymphedema. The fungal colonization of skin in patients with filarial lymphedema may be an important reason for chronic inflammatory disorders.

[Current aspects of chemotherapy of sexually transmitted viral diseases]. / Wspólczesne aspekty chemioterapii zakazen wirusowych przenoszonych droga plciowa.

In recent years, among all sexually transmitted infectious agents, viral infections were indisputably at the head. In this group, genital herpes is one of the substantial infections. Acyclovir, valcyclovir and famcyclovir are the compounds applied in the treatment of Herpes simplex infections. In the therapy with an application of alternative drugs, the possibility of foscarnet should be inquired. These drugs have precise documentation on an application in the treatment of herpetic symptoms of acute infections. However, they do not influence, in radical way, the prevention of relapse of the disease. In spite of their universal and generally accessible application, they also do not influence the interruption of transmission of infection. It seems, that in the nearest perspective, there are hopes associated with introduction of effective and active immunization or, less probable, an introduction of the drug or method of the treatment terminating latency.

Testing the theory of threshold concepts in a context of dental education. Preliminary analysis.

This paper reports on the pilot phase of a phenomenographic study which explores the relationship between teachers' and students' perceptions of the curriculum and theory of threshold concepts, which claims that there are concepts in all disciplines which must be understood, if learners are to progress to a more advanced level of understanding. It is suggested that threshold concepts may represent ways of thinking and practising within disciplines. In this study consideration is given to the troublesome aspects of knowledge as described by David Perkins (1999) and further developed by Meyer and Land (2003). Researcher's intention is to investigate if students experience any conceptual difficulties and what the nature of these might be. Students' and teachers' accounts of how they perceive the dental curriculum might help to verify if there is a relationship between the curriculum and the theory of threshold concepts. Analysis of the troublesome aspects of knowledge may lead to the identification of threshold concepts in the dental curriculum.

Orthotopic bone induction at sites of Moloney murine sarcoma virus inoculation in mice.

Moloney murine sarcoma virus (M-MSV) induces at the site of inoculation in newborn and adult mice and rats various types of sarcoma, including osteosarcoma. The induced tumours are fatal in newborn, whereas sarcomas developed in adult animals regress spontaneously. The regression is mediated mainly by a cellular response. We have now demonstrated that the presence of sarcomas induced by M-MSV is a powerful stimulus for periosteal osteogenesis around tumour masses. Orthotopically induced osteogenesis by M-MSV may serve as a model for local regulation of bone growth and for cell differentiation studies, and may help explain the aetiology of some human bone disorders.

Effect of microwave radiation on cells treated with membrane-injuring substances.

WISH cells grown in vitro were pretreated with subcytotoxic concentrations of digitonin, cortisol and purified bacterial toxins -- staphylococcal beta-haemolysin or Clostridium perfringens alpha-toxin and irradiated with 3 GHz electromagnetic wave (microwaves) at the field power densities 5 or 40 mW/cm2. At 40 mW/cm2 increase in temperature of the culture medium of about 2-3 degrees C was noted, while at 5 mW/cm2 no detectable increase in temperature was found. Control and pretreated WISH cells after irradiation in the microwave field were used for evaluation of their viability, incorporation of tritiated thymidine, glycine and uridine and level of intracellular cyclic AMP. Irradiation with microwaves resulted in lowering of thymidine and glycine incorporation along with changes in the intracellular amount of cAMP (decrease in cells exposed to 5 mW/cm2 and increase in those exposed to 40 mW/cm2). Under both conditions viability of the cultures was normal. Pretreatment of cells with digitonin or purified bacterial toxins followed by irradiation with microwaves resulted in enhancement of the cytotoxic effect with lowering of cell viability, especially after exposition to power density of 40 mW/cm2. Cortisol led to decrease in 3H-glycine and 3H-uridine incorporation into WISH cells, but did not influence the reaction of the cells to microwave radiation. In view of the results presented it may be concluded that substances injuring cell membranes sensitize cell cultures to electromagnetic radiation of the microwave range and may enhance the specific (non-thermal) effect of microwaves.

Virally induced periosteal osteogenesis in mice.

Inoculation of Moloney murine sarcoma virus (M-MSV) into shank muscles of adult NMRI mice resulted in localized sarcoma and periosteal membrane proliferation with subsequent periosteal bone formation. Newly formed bone arose from outer surface of shank bones. Two weeks after M-MSV inoculation the width of bone cortex increased nearly 4 times. The spaces between newly formed bone ossicles were filled with bone marrow. In the later stages these bone marrow cavities were merged with medullar cavities. No extraskeletal bone formation was observed. The regression of M-MSV-induced sarcomas coincides with cessation of the proliferation of bone therefore allowing the maturation and rebuilding of bone. Newly formed bone was not resorbed during a 6-month observation period.