meso-Acetoxymethyl BODIPY dyes for photodynamic therapy: improved photostability of singlet oxygen photosensitizers.

We report two BODIPY based photosensitizers (Br2BOAc and I2BOAc) featuring an acetoxymethyl substituent at the meso-position. These photosensitizers show improved photostability against singlet oxygen, when compared to a BODIPY photosensitizer lacking the acetoxymethyl group. Both compounds were evaluated for photodynamic therapy against HeLa cells and photodynamic inactivation against E. coli bacteria. We show that the compounds readily embed in the lipid membranes of HeLa cervical cancer cells and efficiently induced light-dependent apoptosis at nanomolar concentration. Also, both compounds showed a substantial degree of photoinactivation of E. coli bacteria when used at low micromolar concentrations.

A novel patient-controlled bidirectional palatal lift appliance.

OBJECTIVE: Palatal lift appliances have a role in management of velopharyngeal dysfunction for immobile palates of adequate length where surgery is contraindicated. Conventional appliances involve acrylic/wire work adjustment over successive appointments until they can be tolerated without gagging. A novel appliance has been developed where the lifting plate is incrementally distalized by the patient and vertically adjusted to optimize soft palate positioning. METHOD: The design, construction, and utility of the appliance, which was developed in Dundee Dental Hospital, are described. PARTICIPANTS: The subject was a 12-year-old boy with a variant of Moebius syndrome and velopharyngeal dysfunction. Previous pharyngoplasty had been carried out and further surgery was contraindicated. INTERVENTIONS: The appliance is constructed and fitted and the flexible spring arm is vertically adjusted to lift the soft palate. The screw is turned incrementally at home, extending the lifting plate posteriorly. Videofluoroscopy allows visualization of the appliance and soft palate positioning. MAIN OUTCOME MEASURES/RESULTS: The procedure improved soft palate positioning, as demonstrated by videofluoroscopy, and objective speech outcomes. CONCLUSIONS: The appliance was well tolerated and led to improved speech outcomes for the patient. Adjustments were quick and easy for both clinician and patient. Further studies are needed to definitively determine the efficacy of the appliance.

The impact of a school-based water supply and treatment, hygiene, and sanitation programme on pupil diarrhoea: a cluster-randomized trial.

The impact of improved water, sanitation, and hygiene (WASH) access on mitigating illness is well documented, although impact of school-based WASH on school-aged children has not been rigorously explored. We conducted a cluster-randomized trial in Nyanza Province, Kenya to assess the impact of a school-based WASH intervention on diarrhoeal disease in primary-school pupils. Two study populations were used: schools with a nearby dry season water source and those without. Pupils attending 'water-available' schools that received hygiene promotion and water treatment (HP&WT) and sanitation improvements showed no difference in period prevalence or duration of illness compared to pupils attending control schools. Those pupils in schools that received only the HP&WT showed similar results. Pupils in 'water-scarce' schools that received a water-supply improvement, HP&WT and sanitation showed a reduction in diarrhoea incidence and days of illness. Our study revealed mixed results on the impact of improvements to school WASH improvements on pupil diarrhoea.

Transmucosal fixation of the fractured edentulous mandible.

Transmucosal fixation is a new strategy for the treatment of edentulous mandibular fractures using external fixation principles within the oral cavity. The component parts of this technique are not new. External fixation, locking plates and transmucosal implants represent the foundations of this technique; the authors' development has been to bring these established methods together as a transmucosal intra oral locking plate fixation technique. The first eight patients treated with this technique have achieved bony union, they have no long-term sensory deficit and all patients were able to eat a soft diet with minimal discomfort the day after surgery. The first five of eight patients on long-term review showed bony union confirmed radiographically. For the remainder and subsequent patients, radiographs have not been scheduled at review, in the absence of symptoms.

Clathrin exchange during clathrin-mediated endocytosis.

During clathrin-mediated endocytosis, clathrin-coated pits invaginate to form clathrin-coated vesicles (CVs). Since clathrin-coated pits are planar structures, whereas CVs are spherical, there must be a structural rearrangement of clathrin as invagination occurs. This could occur through simple addition of clathrin triskelions to the edges of growing clathrin-coated pits with very little exchange occurring between clathrin in the pits and free clathrin in the cytosol, or it could occur through large scale exchange of free and bound clathrin. In the present study, we investigated this question by studying clathrin exchange both in vitro and in vivo. We found that in vitro clathrin in CVs and clathrin baskets do not exchange with free clathrin even in the presence of Hsc70 and ATP where partial uncoating occurs. However, surprisingly FRAP studies on clathrin-coated pits labeled with green fluorescent protein-clathrin light chains in HeLa cells show that even when endocytosis is blocked by expression of a dynamin mutant or depletion of cholesterol from the membrane, replacement of photobleached clathrin in coated pits on the membrane occurs at almost the same rate and magnitude as when endocytosis is occurring. Furthermore, very little of this replacement is due to dissolution of old pits and reformation of new ones; rather, it is caused by a rapid ATP-dependent exchange of clathrin in the pits with free clathrin in the cytosol. On the other hand, consistent with the in vitro data both potassium depletion and hypertonic sucrose, which have been reported to transform clathrin-coated pits into clathrin cages just below the surface of the plasma membrane, not only block endocytosis but also block exchange of clathrin. Taken together, these data show that ATP-dependent exchange of free and bound clathrin is a fundamental property of clathrin-coated pits, but not clathrin baskets, and may be involved in a structural rearrangement of clathrin as clathrin-coated pits invaginate.

Contribution of heat shock proteins to cell protection from complement-mediated lysis.

The possible participation of hsc70 and hsp70 in cellular protection from complement damage was studied. Human erythroleukemia K562 cells were pretreated with reagents affecting hsc70 or hsp70, and cell sensitivity to lysis by antibody and human complement was examined. Treatment with deoxyspergualin, an hsc70 inhibitor, sensitized K562 cells to complement lysis, whereas treatment with ethanol, butanol or hemin, inducers of hsc70 synthesis, protected the cells from complement-mediated lysis. Incubation of K562 at either 42 degrees C or with the amino acid analogue L-azetidine-2-carboxylic acid induced synthesis of hsp70, but not of hsc70. The latter treatment also conferred elevated resistance to complement lysis on K562 cells. Pretreatment of K562 cells with sub-lethal doses of complement desensitizes them to lethal complement doses. No effect of sublytic complement on synthesis of hsc70 and hsp70 was found. However, the results demonstrated that complement stress causes translocation of hsc70 from the cytoplasm to the K562 cell surface. Two monoclonal and two polyclonal antibodies identified hsc70 on the surface of intact, viable complement-stressed cells, while antibodies directed to hsp70 did not bind to these cells. Altogether, the results suggest that the heat shock proteins hsc70 and hsp70 play a role in cell defense against complement.

Caenorhabditis elegans auxilin: a J-domain protein essential for clathrin-mediated endocytosis in vivo.

The budding of clathrin-coated vesicles is essential for protein transport. After budding, clathrin must be uncoated before the vesicles can fuse with other membranous structures. In vitro, the molecular chaperone Hsc70 uncoats clathrin-coated vesicles in an ATP-dependent process that requires a specific J-domain protein such as auxilin. However, there is little evidence that either Hsc70 or auxilin is essential in vivo. Here we show that C. elegans has a single auxilin homologue that is identical to mammalian auxilin in its in vitro activity. When RNA-mediated interference (RNAi) is used to inhibit auxilin expression in C. elegans, oocytes show markedly reduced receptor-mediated endocytosis of yolk protein tagged with green fluorescent protein (GFP). In addition, most of these worms arrest during larval development, exhibit defective distribution of GFP-clathrin in many cell types, and show a marked change in clathrin dynamics, as determined by fluorescence recovery after photobleaching (FRAP). We conclude that auxilin is required for in vivo clathrin-mediated endocytosis and development in C. elegans.

Expression of auxilin or AP180 inhibits endocytosis by mislocalizing clathrin: evidence for formation of nascent pits containing AP1 or AP2 but not clathrin.

Although uncoating of clathrin-coated vesicles is a key event in clathrin-mediated endocytosis it is unclear what prevents uncoating of clathrin-coated pits before they pinch off to become clathrin-coated vesicles. We have shown that the J-domain proteins auxilin and GAK are required for uncoating by Hsc70 in vitro. In the present study, we expressed auxilin in cultured cells to determine if this would block endocytosis by causing premature uncoating of clathrin-coated pits. We found that expression of auxilin indeed inhibited endocytosis. However, expression of auxilin with its J-domain mutated so that it no longer interacted with Hsc70 also inhibited endocytosis as did expression of the clathrin-assembly protein, AP180, or its clathrin-binding domain. Accompanying this inhibition, we observed a marked decrease in clathrin associated with the plasma membrane and the trans-Golgi network, which provided us with an opportunity to determine whether the absence of clathrin from clathrin-coated pits affected the distribution of the clathrin assembly proteins AP1 and AP2. Surprisingly we found almost no change in the association of AP2 and AP1 with the plasma membrane and the trans-Golgi network, respectively. This was particularly obvious when auxilin or GAK was expressed with functional J-domains since, in these cases, almost all of the clathrin was sequestered in granules that also contained Hsc70 and auxilin or GAK. We conclude that expression of clathrin-binding proteins inhibits clathrin-mediated endocytosis by sequestering clathrin so that it is no longer available to bind to nascent pits but that assembly proteins bind to these pits independently of clathrin.

The molecular chaperones Hsp90 and Hsc70 are both necessary and sufficient to activate hormone binding by glucocorticoid receptor.

Glucocorticoid receptors must be complexed with Hsp90 in order to bind steroids, and it has been reported that at least three other proteins, Hop, Hsc70, and a J-domain protein (either Hsp40 or Ydj1), are required for formation of active Hsp90-steroid receptor complex. In the present study, we reinvestigated activation of stripped steroid receptors isolated from either L cells or WCL2 cells. Surprisingly, we found, using highly purified proteins, that only Hsp90 and Hsc70 are required for the activation of glucocorticoid receptors in the presence of steroids; in the absence of steroids, either p23 or molybdate are also required as reported previously. Addition of Hop or Ydj1 had no affect on the rate or magnitude of the activation of the stripped receptors, and quantitative Western blots confirmed that neither Hop or Hsp40 were present in our protein preparations or in the stripped receptors. Furthermore, a truncated recombinant Hsp70 that does not bind Hop or Hsp40 was as effective as wild-type Hsp70 in activating stripped receptor. Since Hsc70 does not bind directly to Hsp90 but both proteins bind to Hop, it has been suggested that Hop acts as a bridge between Hsp90 and Hsp70. However, we found that after Hsc70 or Hsp90 bind directly to the stripped receptors, they are fully reactivated by Hsp90 or Hsc70, respectively. We, therefore, conclude that Hsp90 and Hsc70 bind independently to stripped glucocorticoid receptors and alone are sufficient to activate them to bind steroids.

Hsc70 chaperones clathrin and primes it to interact with vesicle membranes.

When Hsc70 uncoats clathrin-coated vesicles in an auxilin- and ATP-dependent reaction, a single round of rapid uncoating occurs followed by very slow steady-state uncoating. We now show that this biphasic time course occurs because Hsc70 sequentially forms two types of complex with the dissociated clathrin triskelions. The first round of clathrin uncoating is driven by formation of a pre-steady-state assembly protein (AP)-clathrin-Hsc70-ADP complex. Then, following exchange of ADP with ATP, a steady-state AP-clathrin-Hsc70-ATP complex forms that ties up Hsc70, preventing further uncoating. This steady-state complex forms only during uncoating in the presence of APs; in the absence of APs, Hsc70 rapidly dissociates from the uncoated clathrin and continues to carry out uncoating. Whether it is complexed with ATP or ADP, the steady-state complex has very different properties from the pre-steady-state complex in that it cannot be immunoprecipitated by anti-clathrin antibodies and is readily dissociated by fast protein liquid chromatography. Remarkably, when the steady-state complex is incubated with uncoated vesicle membranes in ATP, the pre-steady-state complex reforms, suggesting that the clathrin triskelions in the steady-state complex rebind to the membranes and are again uncoated by Hsc70. We propose that Hsc70 not only uncoats clathrin but also chaperones it to prevent it from inappropriately polymerizing in the cell cytosol and primes it to reform clathrin-coated pits.

Role of cyclin G-associated kinase in uncoating clathrin-coated vesicles from non-neuronal cells.

Auxilin is a brain-specific DnaJ homolog that is required for Hsc70 to dissociate clathrin from bovine brain clathrin-coated vesicles. However, Hsc70 is also involved in uncoating clathrin-coated vesicles formed at the plasma membrane of non-neuronal cells suggesting that an auxilin homolog may be required for uncoating in these cells. One candidate is cyclin G-associated kinase (GAK), a 150-kDa protein expressed ubiquitously in various tissues. GAK has a C-terminal domain with high sequence similarity to auxilin; like auxilin this C-terminal domain consists of three subdomains, an N-terminal tensin-like domain, a clathrin-binding domain, and a C-terminal J-domain. Western blot analysis shows that GAK is present in rat liver, bovine testes, and bovine brain clathrin-coated vesicles. More importantly, liver clathrin-coated vesicles, which contain GAK but not auxilin, are uncoated by Hsc70, suggesting that GAK acts as an auxilin homolog in non-neuronal cells. In support of this view, the clathrin-binding domain of GAK alone induces clathrin polymerization into baskets and the combined clathrin-binding domain and J-domain of GAK supports uncoating of AP180-clathrin baskets by Hsc70 at pH 7 and induces Hsc70 binding to clathrin baskets at pH 6. Immunolocalization studies suggest that GAK is a cytosolic protein that is concentrated in the perinuclear region; it appears to be highly associated with the trans-Golgi where the budding of clathrin-coated vesicles occurs. We propose that GAK is a required cofactor for the uncoating of clathrin-coated vesicles by Hsc70 in non-neuronal cells.

A yeast DNA J protein required for uncoating of clathrin-coated vesicles in vivo.

Clathrin-coated vesicles mediate diverse processes such as nutrient uptake, downregulation of hormone receptors, formation of synaptic vesicles, virus entry, and transport of biosynthetic proteins to lysosomes. Cycles of coat assembly and disassembly are integral features of clathrin-mediated vesicular transport (Fig. 1a). Coat assembly involves recruitment of clathrin triskelia, adaptor complexes and other factors that influence coat assembly, cargo sequestration, membrane invagination and scission (Fig. 1a). Coat disassembly is thought to be essential for fusion of vesicles with target membranes and for recycling components of clathrin coats to the cytoplasm for further rounds of vesicle formation. In vitro, cytosolic heat-shock protein 70 (Hsp70) and the J-domain co-chaperone auxilin catalyse coat disassembly. However, a specific function of these factors in uncoating in vivo has not been demonstrated, leaving the physiological mechanism and significance of uncoating unclear. Here we report the identification and characterization of a Saccharomyces cerevisiae J-domain protein, Aux1. Inactivation of Aux1 results in accumulation of clathrin-coated vesicles, impaired cargo delivery, and an increased ratio of vesicle-associated to cytoplasmic clathrin. Our results demonstrate an in vivo uncoating function of a J domain co-chaperone and establish the physiological significance of uncoating in transport mediated by clathrin-coated vesicles.

Interaction between Hsc70 and DnaJ homologues: relationship between Hsc70 polymerization and ATPase activity.

We previously found that, in the presence of ATP, DnaJ homologues catalytically induce formation of a metastable Hsc70 polymer and, similarly, the DnaJ homologue auxilin catalytically induces formation of a metastable Hsc70-clathrin basket complex. Since this suggests that the induction of metastable complexes, which form in ATP but dissociate in ADP, may be a general property of DnaJ homologues, in the present study we investigated in more detail the ability of DnaJ homologues to induce polymerization of Hsc70. This study shows that DnaJ homologues induce polymerization of Hsc70 at the same rate as they induce an initial burst of Hsc70 ATPase activity, showing that polymerization is a specific effect of DnaJ homologue binding to Hsc70. However, polymerization does not always accompany the initial burst of ATPase activity. The dependence of the rates of ATPase activity and polymerization on DnaJ homologue concentration shows that DnaJ homologues bind very weakly to Hsc70 in the presence of ATP and do not bind at all in ADP. Surprisingly, however, under certain conditions the rate of polymerization appears to be independent of Hsc70 concentration, suggesting that polymerization is a first-order reaction, perhaps occurring when two Hsc70 molecules bind to a single DnaJ molecule and then shift their binding to each other. We propose that both the polymerization of Hsc70 by DnaJ homologues and the presentation of substrate by DnaJ homologues to Hsc70 involve the bringing of substrate into proximity with Hsc70 and then independently inducing rapid ATP hydrolysis to cause formation of a metastable Hsc70-substrate complex.

Role of auxilin in uncoating clathrin-coated vesicles.

Clathrin-coated vesicles transport selected integral membrane proteins from the cell surface and the trans-Golgi network to the endosomal system. Before fusing with their target the vesicles must be stripped of their coats. This process is effected by the chaperone protein hsp70c together with a 100K cofactor which we here identify as the coat protein auxilin. Auxilin binds with high affinity to assembled clathrin lattices and, in the presence of ATP, recruits hsp70c. Dissociation of the lattice does not depend as previously supposed on clathrin light chains or on the amino-terminal domain of the heavy chain. The presence of a J-domain at its carboxy terminus now defines auxilin as a member of the DnaJ protein family. In conjunction with hsp70, DnaJ proteins catalyse protein folding, protein transport across membranes and the selective disruption of protein-protein interactions. We show that deletion of the J-domain of auxilin results in the loss of cofactor activity.

Purification of a new clathrin assembly protein from bovine brain coated vesicles and its identification as myelin basic protein.

The multimeric clathrin assembly proteins AP-1 and AP-2 with molecular masses of approximately 270 kDa and the monomeric clathrin assembly proteins AP180 and auxilin with molecular masses of approximately 90 kDa catalyze the assembly of clathrin into artificial clathrin baskets under physiological conditions. We have now identified a much smaller approximately 20-kDa clathrin assembly protein in 0.5 M Tris, pH 7.0, extracts of bovine-brain coated vesicles and purified it to near homogeneity. A polyclonal antibody against this protein did not cross-react with any of the other assembly proteins, and sequencing data suggest that this new protein is similar or identical to myelin basic protein (MBP). At a molar ratio of 3 molecules per clathrin triskelion, MBP catalyzes polymerization of clathrin into artificial baskets that appear structurally similar to the baskets assembled by the other assembly proteins. In addition, like the other baskets, the clathrin-MBP baskets are uncoated by hsp70. MBP represents a significant fraction of the total assembly protein activity present in 0.5 M Tris, pH 7.0, extracts of coated vesicles. It is not clear if it acts as an assembly protein in vivo, but because it is well characterized and easily available, MBP will be a useful protein to investigate the mechanism of clathrin assembly and disassembly in vitro.

Effect of nucleotide on the binding of peptides to 70-kDa heat shock protein.

In previous work we found that bovine brain hsp70 has a single binding site for nucleotide, and that, with ATP at this site, the rates of association and dissociation of clathrin from hsp70 are fast, whereas with ADP at this site, these rates are unmeasurably slow. In the present study we show, first, that peptide C, cytochrome c peptide, and RNase S peptide bind competitively with clathrin, suggesting that they bind to the same site on hsp70, although RNase S peptide binds an order of magnitude more weakly than peptide C and cytochrome c peptide. Second, we show that, with ADP bound to hsp70, as occurs with clathrin, the rate constant for dissociation of peptide markedly decreases compared to the rate constant observed in ATP. In contrast, ADP only slightly decreases the rate of association of peptide. Based on these data we propose a model in which substrates of hsp70 bind to and dissociate from the ATP form of the enzyme, while, following ATP hydrolysis, they are locked onto the ATP form of the enzyme, unable to dissociate until ADP is released and ATP rebinds.

ATPase activity associated with the uncoating of clathrin baskets by Hsp70.

In the presence of ATP, bovine brain hsp70 has been shown to remove clathrin from bovine brain clathrin-coated vesicles in a rapid stoichiometric initial burst followed by slow steady-state uncoating. In addition, it has been found recently that a 100-kDa cofactor is required for hsp70 to uncoat clathrin baskets prepared with the assembly protein AP-2. In this study the ATPase activity associated with uncoating was investigated, with baskets formed from clathrin and assembly proteins. Mixed assembly proteins or assembly protein AP-2 could not be used in ATPase studies because they activated the hsp70 ATPase activity even in the absence of clathrin. However, this was not the case with assembly protein AP180. A stoichiometric initial burst of ATP hydrolysis was found to accompany the initial burst of uncoating of AP180-clathrin baskets by hsp70, with 1 mol of hydrolyzed ATP/mol of released clathrin heavy chain. Furthermore, the presence of a 100-kDa cofactor was needed for both processes. These results suggest that an initial burst of uncoating occurs with all clathrin baskets, that an initial burst of ATP hydrolysis accompanies this initial burst of uncoating, and that a 100-kDa cofactor is required for both.

Novice to expert: an application of the Dreyfus model to management development in health care.

It has been the intent of the authors to describe a management development method which has as its basis a way to differentiate methods for skill development based on levels of skill acquisition. The intent is to provide an efficient and effective framework within which management development can occur as well as to test the utility of the Drefus model in the critical arena of developing management talent in health care environments. Further work and experience with both the model and the skills identified will continue.

Paradigm shifts: theories, models, and tools.

There are many theories and connected tools that have proven to be particularly effective in influencing paradigm shifts. This article has introduced some of each. References listed are useful sources for detailed information. What seems to be clear is that managers should be explicit about the way they characterize their organization. This influences how one measures organizational effectiveness and the selection and application of theories and tools for creating change. The attempt of this article has been to introduce this as a conceptual framework and point to some practical applications in changing organizational thinking.