What makes a 'good group'? Exploring the characteristics and performance of undergraduate student groups.

Group work forms the foundation for much of student learning within higher education, and has many educational, social and professional benefits. This study aimed to explore the determinants of success or failure for undergraduate student teams and to define a 'good group' through considering three aspects of group success: the task, the individuals, and the team. We employed a mixed methodology, combining demographic data with qualitative observations and task and peer evaluation scores. We determined associations between group dynamic and behaviour, demographic composition, member personalities and attitudes towards one another, and task success. We also employed a cluster analysis to create a model outlining the attributes of a good small group learning team in veterinary education. This model highlights that student groups differ in measures of their effectiveness as teams, independent of their task performance. On the basis of this, we suggest that groups who achieve high marks in tasks cannot be assumed to have acquired team working skills, and therefore if these are important as a learning outcome, they must be assessed directly alongside the task output.

Expression of mammalian protein kinase C in Schizosaccharomyces pombe: isotype-specific induction of growth arrest, vesicle formation, and endocytosis.

Mammalian protein kinase C (PKC) isotypes elicit a number of effects on expression in Schizosaccharomyces pombe. A small decrease in growth rate results from PKC-gamma expression, and treatment of these cells with phorbol esters leads to marked growth inhibition and vesicle formation. PKC-delta and -eta expression causes growth inhibition and vesiculation, and the magnitude of both of these effects is increased by phorbol esters. In contrast, PKC-epsilon expression produces growth inhibition but no vesicle accumulation, and this effect is not responsive to phorbol ester. Finally, PKC-zeta has no observable effect. Thus, isotype-specific biological effects are observed. The accumulation of vesicles correlates with phorbol ester-dependent growth inhibition and occurs only with expression of those isotypes that down-regulate in response to phorbol esters in these cells. Antibodies against mammalian clathrin light chain 1a identified clathrin-coated vesicles and up-regulation of clathrin expression in those cells where vesicles accumulate; the increased vesicular traffic includes an element of endocytosis. Thus expression of specific mammalian PKC isotypes up-regulates endocytosis in S. pombe, providing a likely explanation for PKC-mediated receptor internalization in higher eukaryotes.

Selection and preliminary characterization of variant lines of a murine macrophage tumor resistant to the antiproliferative effects of phorbol esters.

Treatment of M5076 wild-type cells with 50 ng/ml of 12-O-tetradecanoylphorbol-13-acetate (TPA) almost completely inhibited cellular proliferation. Continuous culture in the presence of TPA was used to derive four lines, one polyclonal (TPAR) and three clonally derived (TPAR-1, -2, and -3), which exhibited variable resistance to the antiproliferative effects of phorbol esters. Protein kinase C (PKC) activation and c-fos expression in wild-type cells and the stably resistant line (TPAR-3) were examined after phorbol ester treatment. Both lines exhibited a comparable rapid and transient induction of c-fos mRNA expression, but induction of c-fos protein was reduced markedly in the TPAR-3 cells. Similarly in both cell lines, prolonged culture in phorbol ester produced down-regulation of PKC, as measured by inducible Mr 80,000 phosphorylation and an in vitro PKC assay. This decrease in PKC levels was paralleled by a decrease in c-fos mRNA and protein induction. Thus, c-fos expression in both wild-type and TPAR-3 cells is a consequence of PKC activation, and the development of resistance to TPA-antiproliferative effects in the TPAR-3 cell line was not linked causally to alterations in PKC levels or the c-fos mRNA induction response. The malignant capacity of the TPAR line was not reduced relative to wild-type cells. PKC activation and c-fos mRNA expression do not appear to determine changes in the in vivo or in vitro growth behavior of M5076 cells, whereas variations in c-fos protein expression may determine the anti-proliferative response to tumor-promoting phorbol esters.

Protein kinase C-induced stimulation or inhibition of cellular proliferation in a murine macrophage tumor cell line.

M5076, a tumorigenic murine macrophage cell line, demonstrates diverse proliferative responses to a panel of protein kinase C activators. Thus, the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate and mezerein potently inhibit cellular proliferation (by greater than 90%), whereas the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol markedly stimulates proliferation of serum-starved, quiescent M5076 cells. Another DG analogue, 1,2-dioctanoyl-sn-glycerol, has no effect on growth. However, all of these agents induce expression of c-fos oncogene mRNA levels to a similar magnitude and activate protein kinase C as determined by Mr 80,000 phosphorylation. Levels of c-fos protein induced by these treatments were markedly different with the antiproliferative agents producing greater c-fos protein levels.

Differential localization of protein kinase C isotypes in equine eosinophils and neutrophils.

Phorbol esters, which activate protein kinase C (PKC), stimulate equine eosinophil superoxide production and adherence. After showing that superoxide production could be inhibited by the nonselective PKC inhibitors, staurosporine and bisindolymaleimide I, the PKC isotypes in equine eosinophils were characterized, because evidence suggests that individual isotypes may play distinct roles in regulating eosinophil function. Western blots demonstrated that equine eosinophils expressed PKC alpha, beta, delta, epsilon, iota, and zeta. However, unlike the equine neutrophil, the majority of the PKC was detected in the particulate fraction of the cell. Despite this unusual location, the PKC in equine eosinophils was activatable, suggesting that it is functionally competent. The regulatory role of PKC in equine eosinophils may reflect the association of activity with the particulate fraction and the profile of isotype expression.

A phorbol ester-responsive PKC-zeta generated by fusion with the regulatory domain of PKC-delta.

A hybrid molecule generated by fusing the regulatory domain of PKC-delta with the catalytic domain of PKC-zeta is, like PKC-delta but unlike PKC-zeta, a phorbol ester-dependent enzyme. However, the substrate specificity of this hybrid resembles that of PKC-zeta. Expression of mammalian PKC-delta, but not PKC-zeta, in the fission yeast Schizosaccharomyces pombe causes growth retardation and phorbol esters amplify the PKC-delta phenotype without affecting that of PKC-zeta (Goode et al., submitted). The chimaeric molecule also inhibited growth and this effect was phorbol-ester dependent. Both the hybrid and PKC-delta holoenzyme, in contrast to PKC-zeta, down-regulate upon prolonged exposure to phorbol esters in vivo. Thus, this hybrid retains the regulatory properties conferred by PKC-delta but the catalytic properties of PKC-zeta. This regulatable chimaeric molecule will be useful in assessing the function of PKC-zeta.

Protein kinase C (PKC) isotype profile in eosinophils from ponies with sweet itch and role in histamine-induced eosinophil activation.

Eosinophils have been implicated in the pathogenesis of the seasonal equine allergic skin disease, sweet itch. Protein kinase C (PKC) is involved in regulating eosinophil function and antigen challenge has been reported to alter PKC isotype expression in blood eosinophils from allergic human subjects. Here we have compared the pattern of PKC isotype expression in eosinophils from sweet itch ponies with that in cells from normal ponies both during the active and inactive phases of the disease. A role for PKC in histamine-induced eosinophil activation was also investigated. Conventional PKCs alpha and beta, novel PKCs delta and epsilon and atypical PKCs iota and zeta were identified in eosinophils pooled from four allergic ponies during the inactive phase, when no clinical signs were evident. The PKC isotypes, like those in eosinophils from normal ponies, were located primarily in the particulate fraction of the cell. Isotype expression in cells from normal and allergic animals did not appear to be different. In contrast, during the active phase of the disease, when the sweet itch ponies had clinical signs, the expression of PKCs beta, epsilon and iota in eosinophils from these animals appeared to be increased relative to that in cells from normal ponies. When PKC expression in eosinophils from five individual normal and sweet itch ponies was compared, small, but statistically significant, increases in PKC epsilon and PKCdelta expression were evident in eosinophils from the sweet itch ponies during the active and inactive phases, respectively. The non-selective PKC inhibitors, staurosporine and Ro31-8220, significantly reduced histamine-induced superoxide production. Use of Gö6976, an inhibitor of conventional PKCs, suggested that PKCalpha and/or beta were involved and that there was significantly greater inhibition of the response in eosinophils obtained from sweet itch ponies during the active phase. There was no significant difference in histamine-induced superoxide production by eosinophils from allergic and normal ponies and the functional significance of the increased PKC isotype expression in eosinophils from sweet itch ponies relative to that in cells from healthy animals remains to be established.

Biochemical and functional assessment of equine lymphocyte phosphodiesterases and protein kinase C.

Lymphocytes play an important role in allergic inflammation and have been implicated in the pathogenesis of equine allergic skin and respiratory disease. Targeting intracellular signalling pathways in human lymphocytes has demonstrated a role for both phosphodiesterase and protein kinase C in cell activation. The aim of this study was to measure total cyclic nucleotide hydrolysing phosphodiesterase activity and to identify the phosphodiesterase and protein kinase C isoenzymes present in equine lymphocytes. The functional significance of these isoenzymes was then investigated by examining their role in peripheral blood mononuclear cell proliferation using isoenzyme selective inhibitors. Total cyclic adenosine monophosphate hydrolysing phosphodiesterase activity was double that of cyclic guanosine monophosphate (30+/-2 pmol/min mg versus 16+/-3 pmol/min mg for cyclic adenosine and cyclic guanosine monophosphate phosphodiesterase activity, respectively). Evidence for the presence of PDE1, 3, 4 and 5 was obtained and PKCalpha, beta, delta, eta, iota, theta and zeta were identified. Selective inhibitors of PDE4, PKCdelta and conventional PKCs alpha and beta caused significant inhibition of mitogen-induced peripheral blood mononuclear cell proliferation. This study demonstrates a functional role for specific signalling isoenzymes and suggests that, in the context of allergic inflammation, targeting inflammatory cells involved in disease pathogenesis with relevant isoenzyme inhibitors may have therapeutic potential.

Cloning, expression and biological activity of equine interleukin (IL)-5.

The cytokine, interleukin (IL)-5 stimulates eosinophil differentiation, activation and survival and can prime these cells, increasing the response to other mediators. In view of its many effects on eosinophils, IL-5 has been implicated in the pathogenesis of allergic disease in man. Here we report the cloning of equine IL-5 and expression of the recombinant protein by transfection of Chinese hamster ovary (CHO) cells. The cloned cDNA sequence consisted of 405 nucleotides and encoded a protein of 135 amino acids. There is >85% identity with feline, bovine, ovine, canine, and human IL-5 sequences at the nucleotide and protein level. Supernatants containing equine IL-5 were also examined for biological activity. CHO supernatant containing equine recombinant (eqr) IL-5, like the human ortholog (hrIL-5), induced concentration dependent equine eosinophil adherence to autologous serum-coated plastic (9.7+/-1.5% with a 1:100 dilution of eqrIL-5 and 9.1+/-1.6% adherence with 1 nM hrIL-5; n = 4). The eqr protein also caused concentration dependent superoxide production (11.9+/-2.4 nmol (reduced cytochrome (cyt) C)/10(6) cells at a 1:50 dilution, n = 4). In contrast, hrIL-5 only caused significant superoxide production when diluted in conditioned CHO medium, an effect that was inhibited by the anti-human mAb, TRFK5 (4.4+/-0.3 versus 0.3+/-0.4 nmol/10(6) cells for 0.5 nM hrIL-5 in the presence of the isotype matched IgG1 control (10 microM) and TRFK5 (10 microM), respectively). TRFK5 also significantly inhibited hrIL-5 induced adherence at concentrations of 0.3 microg/ml and above but had no significant inhibitory effect on either superoxide or adherence caused by eqrIL-5. These results demonstrate that equine IL-5 expressed by CHO cells stimulates equine eosinophils, suggesting that this cytokine could play a role in eosinophil recruitment and activation in equine allergic disease. The anti-human and murine moAb TRFK5 does not appear to recognise the equine protein.

The role of protein kinase C in regulating equine eosinophil adherence and superoxide production.

OBJECTIVE: To determine if protein kinase C (PKC) regulates equine eosinophil function. MATERIAL OR SUBJECTS: Blood eosinophils were obtained from healthy ponies. METHODS: IL-5- and histamine-induced adherence to serum-coated plastic was measured as the eosinophil peroxidase content of adherent cells and serum treated zymosan (STZ)-and IL-5-induced superoxide production by the reduction of cytochrome C. Eosinophil PKC activity was quantitated as the rate of transfer of (32)P from ATP to substrate. The effects of Ro31-8220 (isotype non-selective PKC inhibitor), Go6976 (conventional PKC inhibitor), and rottlerin (PKCdelta inhibitor) were determined by ANOVA and Bonferroni's or Dunnett's test. RESULTS: Ro31-8220 and Go6976 reduced superoxide production whereas only Go6976 inhibited adherence. Rottlerin inhibited histamine-induced adherence and increased STZ-induced superoxide production. Ro31-8220 and Go6976, but not rottlerin, inhibited PKC activity. CONCLUSIONS: PKC is involved in regulating equine eosinophil adherence and superoxide production. The role of PKCdelta appears to depend upon the stimulus used and response measured.

Protein kinase C levels and protein phosphorylation associated with inhibition of proliferation in a murine macrophage tumor.

Treatment of M5076 tumor cells with the phorbol estes 12-O-tetradecanoylphorbol 13-acetate (TPA) and phorbol 12,13 dibutyrate (PdBu) inhibited cellular proliferation, whereas 1,2-dioctanoyl-glycerol (DiC8) and 1-oleoyl2-acetyl-glycerol (OAG) did not affect cell growth. Inhibition of cellular proliferation in this cell line appears to be a consequence of protein kinase C (PKC) down-regulation since phorbol esters, but not a single application of diacylglycerols (DGs) down-regulated cellular PKC levels. By repeated application of DGs, PKC down-regulation was achieved and correlated with inhibition of proliferation. Phorbol ester-induced PKC down-regulation was reversible, upon removal of the phorbol ester, and the reappearance of PKC was associated with resumption of proliferation. The mitogenic responsiveness of these cells to added serum depended upon cellular PKC levels. Phorbol esters also caused the phosphorylation of two proteins which were not phosphorylated in response to DG treatment. Inhibition of growth of M5076 cells appears to be associated with phosphorylation of two novel proteins and/or PKC down-regulation.

Protein kinase C (PKC)-induced PKC down-regulation. Association with up-regulation of vesicle traffic.

Phorbol esters cause long term activation of protein kinase C (PKC) and frequently the down-regulation of PKC protein levels in mammalian cells. Mammalian PKC-gamma, -delta, and -eta down-regulated in response to phorbol esters when expressed in Schizosaccharomyces pombe. However, PKC-epsilon does not down-regulate in S. pombe, in contrast to the behavior of this isotype in mammalian cells. Co-expression of PKC-gamma or -delta with PKC-epsilon in S. pombe renders PKC-epsilon susceptible to down-regulation. A protein kinase defective form of PKC-delta does not down-regulate efficiently in S. pombe but, like PKC-epsilon, is susceptible when co-expressed with PKC-gamma or full-length PKC-delta. Thus, down-regulation is a consequence of the catalytic function of certain PKC isotypes with other isotypes being affected in trans. PKC down-regulation parallels a striking accumulation of vesicles in S. pombe, suggesting a direct relationship between these events.