Clarithromycin transport by gingival fibroblasts and epithelial cells

Macrolide antibiotics penetrate cells, but the mechanism by which this occurs is unclear. The objective of this study was to characterize the mechanisms of clarithromycin uptake by gingival fibroblasts and oral epithelium. Cultured human gingival fibroblasts and SCC-25 cells were incubated with [(3)H]-clarithromycin. We assayed clarithromycin transport by measuring cell-associated radioactivity over time. Fibroblasts and epithelial cells rapidly accumulated clarithromycin, attaining steady-state intracellular concentrations within 15 minutes. Incubation in medium containing 2 mug/mL clarithromycin yielded steady-state intracellular concentrations of 75.8 mug/mL in fibroblasts and 6.6 mug/mL in SCC-25 cells. Clarithromycin transport exhibited Michaelis-Menten kinetics and was inhibited below 37 degrees C. The Michaelis constants for fibro-blasts and SCC-25 cells were 78.4 and 227 mug/mL, respectively, while the maximum transport velocities were 264 and 381 ng/min/10(6) cells, respectively. Thus, both types of cells take up clarithromycin via a concentrative active transport system. By increasing intracellular clarithromycin levels, this system may enhance the effectiveness of clarithromycin against invasive periodontal pathogens.

Accumulation of topical naproxen by cultured oral epithelium

Topically administered non-steroidal anti-inflammatory drugs (NSAIDs) inhibit periodontal bone loss, but little is known about the mechanism by which they penetrate oral epithelium. Active transporters could potentially play a role in this process. In this study, we used a cell line derived from oral epithelium to investigate a role for transporters and to characterize conditions that enhance epithelial penetration. Using fluorescence to monitor uptake, we demonstrated that SCC-25 cell monolayers transport naproxen with a Michaelis constant (K(m)) and maximum velocity (V(max)) of 164 microg/mL and 0.94 ng/min/microg protein, respectively. At steady state, the intra-cellular/extracellular concentration ratio was 3.4. Naproxen accumulation was more efficient at acidic pH than under neutral or alkaline conditions. Small proportions of glycerol, Pluronic F-127, and glucosylceramide enhanced naproxen entry. The individual and combined effects of glycerol and Pluronic F-127 were of lesser magnitude than those obtained with glucosylceramide or at pH 6.3. Thus, SCC-25 cells possess transporters for naproxen.

Oral clonidine pre-treatment and diazepam/meperidine sedation

Clonidine has recently been used as a pre-operative medication and sedative/anxiolytic drug. Its extended duration of action makes it suitable for longer procedures. In this randomized, crossover, placebo-controlled clinical trial, we characterized the effects of oral clonidine pre-treatment on intravenous diazepam/meperidine sedation using the bi-spectral index (BIS) in 13 participants. Clonidine significantly increased the numbers of BIS-depressed readings and percent memory loss during sedation, while reducing total diazepam and post-operative analgesic dosages by 44% and 55%, respectively. Systolic, diastolic, and mean arterial blood pressures, as well as pulse rates, were reduced. Respiratory rate, oxygen saturation, end-tidal CO(2), and recovery from sedation were unchanged. Participants, surgeons, and sedationists preferred clonidine over the placebo. Clonidine pre-treatment increased and prolonged sedation and amnesia and stabilized vital signs while significantly decreasing diazepam and post-operative analgesic usage. These results suggest that pre-operative clonidine administration could be a useful supplement to intravenous sedation for dental procedures of long duration.

Periodontal bone loss associated with an improper flossing technique: a case report

PURPOSE

This article documents a case in which soft tissue and bone damage was associated with a long-standing habit of improper flossing.

CASE DESCRIPTION

A 33-year-old patient with excellent oral hygiene presented with gingival clefting and an unusual pattern of moderate angular bone loss at several sites. Previous radiographs suggested that some bony lesions had been present for more than 13 years. Examination revealed no evidence that the osseous defects were related to chronic periodontitis or occlusal trauma. The focus of treatment for these chronic injuries was teaching the patient an atraumatic flossing technique.

CONCLUSION

As the lesions had gone undiagnosed for many years, this case underscores the need to look for clinical signs of floss-induced damage during periodic examinations.

Modulation of gingival fibroblast minocycline accumulation by biological mediators

Gingival fibroblasts actively accumulate tetracyclines, thereby enhancing their redistribution from blood to gingiva. Since growth factors and pro-inflammatory cytokines regulate many fibroblast activities, they could potentially enhance fibroblast minocycline accumulation. To test this hypothesis, we treated gingival fibroblast monolayers for 1 or 6 hours with platelet-derived growth factor-BB (PDGF), fibroblast growth factor-2 (FGF), transforming growth factor-beta1 (TGF), or tumor necrosis factor-alpha (TNF). Minocycline uptake was assayed at 37 degrees by a fluorescence method. All 4 factors significantly enhanced minocycline uptake (P < or = 0.008, ANOVA), primarily by increasing the affinity of transport. Treatment for 6 hours with 10 ng/mL FGF, PDGF, TGF, or TNF enhanced fibroblast minocycline uptake by 19% to 25%. Phorbol myristate acetate enhanced fibroblast minocycline uptake by 28%, suggesting that protein kinase C plays a role in up-regulating transport. These effects on transport provide a mechanism by which systemic tetracyclines could be preferentially distributed to gingival wound or inflammatory sites.

Effect of niobium content on the microstructure and thermal properties of fluorapatite glass-ceramics

Niobium oxide has been shown to improve biocompatibility and promote bioactivity. The purpose of this study was to evaluate the effect of niobium oxide additions on the microstructure and thermal properties of fluorapatite glass-ceramics for biomedical applications. Four glass-ceramic compositions with increasing amounts of niobium oxide from 0 to 5 wt % were prepared. The glass compositions were melted at 1,525 degrees C for 3 h, quenched, ground, melted again at 1,525 degrees C for 3 h and furnace cooled. The coefficient of thermal expansion was measured by dilatometry. The crystallization behavior was evaluated by differential thermal analysis. The nature of the crystalline phases was investigated by X-ray diffraction. The microstructure was studied by SEM. In addition, the cytotoxicity of the ceramics was evaluated according to the ASTM standard F895--84. The results from X-ray diffraction analyses showed that fluorapatite was the major crystalline phase in all glass-ceramics. Differential thermal analyses revealed that fluorapatite crystallization occurred between 800 and 934 degrees C depending on the composition. The coefficient of thermal expansion varied from 7.6 to 9.4 x 10(-6)/ degrees C. The microstructure after heat treatment at 975 degrees C for 30 min consisted of submicroscopic fluorapatite crystals (200--300 nm) for all niobium-containing glass-ceramics, whereas the niobium-free glass-ceramic contained needle-shaped fluorapatite crystals, 2 microm in length. None of the glass-ceramics tested exhibited any cytotoxic activity as tested by ASTM standard F895--84.

Short-chain carboxylic acids produced by gram-negative anaerobic bacteria can accelerate or delay polymorphonuclear leukocyte apoptosis in vitro

BACKGROUND

Short-chain carboxylic acids (SCCA) are metabolic byproducts of anaerobic subgingival bacteria associated with human periodontal disease. We examined the effect of 4 SCCA (butyric, propionic, succinic, and lactic acids) on human polymorphonuclear leukocyte (PMN) apoptosis over the range of concentrations (1 to 30 mM) found in the diseased periodontium.

METHODS

PMN suspensions were incubated at 37 degrees C with medium alone (control) or one of the 4 SCCA at concentrations of 1, 5, or 30 mM. Aliquots were withdrawn hourly to assess apoptosis and viability by fluorescence microscopy.

RESULTS

Relative to untreated controls, PMN incubated for at least 5 hours with 1 mM butyric or propionic acids exhibited significant delays in apoptosis (P<0.05), while those incubated with succinic or lactic acids exhibited no significant differences from controls (P>0.05). At a concentration of 5 mM, propionic, succinic, and lactic acids had little effect on apoptosis (P>0.05), but butyric acid significantly accelerated apoptotic changes (P<0.05). At 30 mM, all SCCA except lactic acid significantly accelerated apoptosis (P<0.05). Incubation with SCCA did not adversely affect cell viability (typically >98%). Lysates from PMN incubated 6 hours with 30 mM butyric or propionic acids contained significantly more caspase-3 activity than lysates from untreated control PMN (P<0.05). Moreover, pretreatment with a specific inhibitor of caspase-3 blocked acceleration of PMN apoptosis by butyric or propionic acids (P<0.05).

CONCLUSION

Low concentrations of butyric or propionic acids delay PMN apoptosis and extend their functional lifespan, while higher concentrations accelerate apoptosis through a mechanism that appears to involve caspase-3.

Excision and repair of the peripheral ossifying fibroma: a report of 3 cases

BACKGROUND

The peripheral ossifying fibroma (POF), one of the most common gingival lesions, has a recurrence rate of nearly 20%. To minimize the reappearance of this lesion, it must be completely excised. In the maxillary anterior region, total excision of a POF can result in an unsightly gingival defect.

METHODS

Three cases are presented in which a POF was excised from the gingiva facial to a maxillary central incisor. One of these lesions had previously undergone 2 cycles of conservative excision and recurrence. In all cases, the lesions were excised down to bone. Each of the resulting gingival defects was repaired by a distinct plastic surgery procedure, including a laterally positioned flap, a subepithelial connective tissue graft, and a coronally positioned flap.

RESULTS

The defects resulting from the biopsies were satisfactorily repaired. The patients were followed over postsurgical intervals of 10 to 30 months. None of the lesions recurred.

CONCLUSIONS

It is customary to manage POF by aggressive excisional biopsy. Several different surgical approaches may potentially be used to repair the resultant gingival defect and minimize patient esthetic concerns.

Fluoroquinolone transport by human monocytes: characterization and comparison to other cells of myeloid lineage

Human monocytes transport and accumulate ciprofloxacin and other fluoroquinolones. Although little is known about the mechanisms of transport, we expected monocytes to be similar to other cells of myeloid lineage. In the present study, monocyte fluoroquinolone transport was characterized and compared to the corresponding transport pathways of human polymorphonuclear leukocytes (PMNs) and HL-60 cells. Ciprofloxacin transport by monocytes was saturable, temperature dependent, sodium independent, and relatively insensitive to pH. Quiescent monocytes transported ciprofloxacin with a K(m) of 171 microg/ml and a V(max) of 32.7 ng/min/10(6) cells. Adenine competitively inhibited ciprofloxacin transport by quiescent monocytes (K(i) = 3.8 mM), but nucleosides had no significant inhibitory effect. In all of these respects, transport by monocytes was similar to that observed for quiescent PMNs and immature HL-60 cells. Unlike PMNs, however, monocytes and immature HL-60 cells did not exhibit dramatically enhanced ciprofloxacin transport when activated by phorbol myristate acetate (PMA). Consistent with this finding, HL-60 cells committed to granulocytic differentiation exhibited a significant component of PMA-inducible ciprofloxacin transport activity, while HL-60 cells committed to monocytic differentiation did not. In PMNs, the PMA-inducible component of transport appeared to be mobilized from a granule compartment, since its activity could be modulated by agents that enhance or inhibit stimulated degranulation. Thus, quiescent monocytes, PMNs, and HL-60 cells take up ciprofloxacin via similar energy-dependent transport mechanisms. Unlike granulocytes, monocytes do not express a second, higher-affinity pathway for ciprofloxacin accumulation when they are activated by PMA.

The role of protein kinase C and calcium in induction of human polymorphonuclear leukocyte IL-1 beta gene expression by GM-CSF

At infection sites, synthesis of interleukin (IL-)1beta by polymorphonuclear leukocytes (PMNs) facilitates the recruitment of inflammatory cells and enhances the inflammatory response. We investigated the role of protein kinase C (PKC) and Ca2+ in the induction of PMN IL-1beta gene expression by GM-CSF. The PKC inhibitors chelerythrine and H7 blocked induction of IL-1beta mRNA expression in human PMNs. HA1004, an H7 analogue with little activity towards PKC, had no inhibitory effect. Similarly, H7 blocked IL-1beta transcription in nuclear run-on analysis, while HA1004 had little effect. The intracellular Ca2+ chelator BAPTA/AM inhibited induction of IL1beta mRNA accumulation and transcription by GM-CSF. At concentrations similar to those used to inhibit IL-1beta gene expression, H7, chelerythrine, and BAPTA all inhibited substrate phosphorylation by PKC isolated from PMN lysates. Thus, PKC and Ca2+ are potential targets for modulating an important PMN immunoregulatory function.

Mechanisms of fluoroquinolone transport by human neutrophils

Neutrophils accumulate ciprofloxacin and other fluoroquinolones, a process that enhances the killing of intracellular pathogens and could facilitate the delivery of these agents to infection sites by migrating neutrophils. The mechanisms by which transport occurs have not been characterized. In the present study, quiescent neutrophils transported ciprofloxacin with an observed K(m) of 167 microgram/ml (501 microM) and a maximum velocity of 25.2 ng/min/10(6) cells. When neutrophils were stimulated with phorbol myristate acetate (PMA), a second component of ciprofloxacin transport was induced. This pathway had an apparent K(m) of 9.76 microgram/ml (29.3 microM) and a maximum velocity of 59.3 ng/min/10(6) cells. Transport by both pathways was Na(+) independent. Ciprofloxacin transport by quiescent cells was relatively insensitive to pH and N-ethylmaleimide but was competitively inhibited by adenine (K(i) = 1.55 mM). Papaverine, a benzylisoquinoline known to inhibit nucleobase transport, also inhibited ciprofloxacin transport by quiescent cells. In contrast, transport by PMA-stimulated cells was enhanced at pH 8.2, inhibited at pH 6.2, and blocked by N-ethylmaleimide. Cationic and neutral amino acids and cystine competitively inhibited ciprofloxacin transport by PMA-stimulated neutrophils (K(i) = 158 microM for ornithine) but had little effect on quiescent cells. PMA-activated transport was not inhibited when the Na(+) in the medium was replaced with K(+) or Li(+), and the pattern of inhibition by cationic and neutral amino acids was similar. In summary, neutrophils continuously transport ciprofloxacin via a transport pathway shared by adenine. Activation by PMA induces a separate, higher-affinity transport pathway shared by a broad scope of amino acids. Neutrophils utilize one or both of these mechanisms to transport other fluoroquinolones.

Porphyromonas gingivalis lipopolysaccharide delays human polymorphonuclear leukocyte apoptosis in vitro

Apoptosis (programmed cell death) is a mechanism by which superfluous or damaged cells undergo changes that lead to selective removal from organ systems by phagocytic cells. Certain bacterial products delay apoptosis in neutrophils (PMNs). In this study, PMNs were incubated for up to 8 h with varying concentrations of lipopolysaccharide (LPS), lipid A or capsular polysaccharide isolated from 3 strains of Porphyromonas gingivalis (Pg) (strains HG-184, A7A1-28 and 381). Assay runs included controls containing cells and medium but no bacterial products. Fluorescence microscopy was used to evaluate apoptotic changes. PMNs exhibited a time-dependent increase in the number of apoptotic cells. When cells were cultured in the presence of LPS from any of the 3 Pg strains, apoptosis was delayed in a dose-dependent fashion (p < 0.05). The effects of these LPS preparations were similar to each other and to Escherichia coli 0111:B4 LPS. Lipid A from the 3 Pg strains also delayed apoptosis (p < 0.05), but was less potent than LPS or synthetic lipid A. Capsular polysaccharide had no significant effect on apoptosis (p > 0.05). Thus, LPS and lipid A from P. gingivalis appear to modulate the functional lifespan of PMNs. This could potentiate the inflammatory and destructive components of periodontal diseases.

Polyamines found in the inflamed periodontium inhibit priming and apoptosis in human polymorphonuclear leukocytes

BACKGROUND

Polymorphonuclear leukocytes (PMNs) are exposed to high concentrations of polyamines in the inflamed periodontium and possess a transport system for taking up these compounds. Previous studies suggest that polyamines are involved in priming of the PMN respiratory burst by tumor necrosis factor-alpha (TNF-alpha) and can stabilize DNA against degradation. The purpose of this study was to determine whether exogenous polyamines can modulate priming by TNF-alpha or delay nuclear changes associated with PMN apoptosis (programmed cell death).

METHODS

Isolated human PMNs were incubated with putrescine or spermidine in vitro. Superoxide generation was measured with a cytochrome C reduction assay, and apoptotic changes were assessed by fluorescence microscopy (after cell staining with acridine orange and ethidium bromide).

RESULTS

Incubation with 1 mM putrescine for 1 hour inhibited superoxide production by TNF-primed PMNs by 20%, but enhanced the production of superoxide by unprimed cells by 38%. Both effects were dose dependent and statistically significant (P <0.03, repeated measures ANOVA and Dunnett's test). Spermidine had no significant effects on PMN oxidative function. With regard to apoptosis, 1 mM putrescine or spermidine produced a statistically significant reduction in the proportion of apoptotic PMNs within 6 to 9 hours (P <0.05). In cells incubated for 7 hours with 300 microM putrescine or spermidine, the proportion of apoptotic cells was approximately 30% lower than in untreated controls (P <0.05, Dunnett's test). The delay of apoptosis by spermidine was less profound than that produced by TNF-alpha and was not additive to the effects of this cytokine.

CONCLUSIONS

Polyamines could potentially impair the priming of PMN oxidative function by TNF-alpha at sites where this cytokine is present. In the absence of TNF-alpha, polyamines could enhance PMN superoxide release and enhance the maintenance of PMN function in the periodontal pocket.

An inhibitor of ornithine decarboxylase antagonizes superoxide generation by primed human polymorphonuclear leukocytes

Tumor necrosis factor-alpha (TNF-alpha) induces a rapid increase in polymorphonuclear leukocyte (PMN) polyamine content which appears to be required for optimal priming of the respiratory burst. The objective of the present study was to determine whether inhibition of polyamine biosynthesis modifies PMN responses to lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte colony-stimulating factor (G-CSF). Treatment with alpha-difluoromethylornithine (DFMO), a selective inhibitor of the rate-limiting biosynthetic enzyme ornithine decarboxylase, produced dose-dependent inhibition of the respiratory burst in PMNs that were primed by these agents and subsequently activated by formyl-Met-Leu-Phe (fMLP). However, DFMO did not significantly inhibit fMLP-stimulated superoxide generation or alter the induction of PMN adhesion and interleukin-1 beta (IL-1 beta) mRNA expression by LPS or GM-CSF. Antagonism of priming by DFMO correlated with a dose-dependent attenuation of fMLP-induced intracellular Ca2+ mobilization (r > or = 0.96). Since Ca2+ plays an important role in modulating the respiratory burst in primed PMNs, this could, in part, account for the selective effects of DFMO.

Regulation of ciprofloxacin uptake in human promyelocytic leukemia cells and polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs) actively internalize ciprofloxacin, a capability that can enhance killing of intracellular bacteria and facilitate delivery of the antimicrobial agent to infection sites by migrating PMNs. In this study we investigated mechanisms for up-regulation of this process. Activation with N-formyl-methionyl-leucyl-phenylalanine (fMLP; 100 nM) enhanced PMN ciprofloxacin uptake by 50% (P < 0.05). Phorbol myristate acetate (PMA; > or = 10 nM) enhanced uptake by at least 36-fold, mainly by stimulating an increase in the Vmax of the ciprofloxacin transporter. This effect of PMA was inhibited by antagonists of protein kinase C (H7 and chelerythrine) and the mitogen-activated protein kinase cascade downstream (PD 098059). Under resting and PMA-activated conditions, ciprofloxacin uptake by immature human promyelocytic leukemia (HL-60) cells was much lower than in PMNs. However, when HL-60 cells were induced to mature into PMN-like cells, their ciprofloxacin uptake activity increased markedly. These findings implicate a role for protein kinase C in up-regulation of the ciprofloxacin transporter and suggest that myeloid cells acquire an enhanced ability to take up ciprofloxacin as they mature to end-stage PMNs.

pH changes observed in the inflamed gingival crevice modulate human polymorphonuclear leukocyte activation in vitro

Previous studies have noted a positive correlation between gingival inflammation and crevicular pH, which reportedly varies from 6.5 to 8.5. In the present study, we characterized the manner in which deviation from the "physiological" pH of blood (7.2) influences activation of chemotaxis, phagocytosis, superoxide generation, and degranulation by human polymorphonuclear leukocytes (PMNs). Purified PMNs were suspended in HEPES-buffered balanced salts solutions adjusted to pH 6.7, 7.2, 7.7, or 8.2. In a modified Boyden chamber, the chemotactic response to fMet-Leu-Phe was maximal at pH 7.2. In comparison, chemotaxis was significantly depressed at pH 7.7 and pH 8.2 (P < 0.05), but was not significantly different at pH 6.7. Activation of the respiratory burst by fMet-Leu-Phe was optimal at pH 7.2, but was significantly depressed at pH 6.7 and 8.2 (P < 0.05). pH had little effect on N-acetyl-beta-glucosaminidase release from primary granules. However, lactoferrin release from the secondary granules of fMet-Leu-Phe-activated PMNs was significantly lower at pH 7.2 than at pH 6.7 or 8.2 (P < 0.05). Moreover, phagocytosis of opsonized bacteria was significantly lower at pH 7.2 than at pH 7.7. In addition to these effects on functional activation, extracellular pH influenced the magnitude of intracellular Ca2+ mobilization. Peak fMet-Leu-Phe-induced Ca2+ levels were significantly higher at pH 8.2 than at pH 7.2 (P < 0.01). These findings suggest that the pH of the periodontal environment can selectively influence PMN activation, thereby altering the balance between bacteria and the host response.

Gangliosides inhibit PDGF-induced signal transduction events in U-1242 MG human glioma cells

In this study we investigated the responses of intracellular calcium ([Ca2+]i) and protein kinase C (PKC) to PDGF in U-1242 MG cells. PDGF-BB stimulated [3H]PDBu binding approximately 2-3 fold. This response was inhibited by preincubating the cells with an inhibitor of phospholipase C (PLC), U73122, suggesting that PLC mediates the induction of PKC translocation by PDGF. PDGF also increased the concentration of [Ca2+]i that was attenuated in a calcium-free medium. This indicates that PDGF-induced elevation of [Ca2+]i is mainly due to influx of extracellular calcium. PDGF-stimulated translocation of PKC was inhibited by the intracellular calcium buffer BAPTA/AM. All gangliosides studied except GM3 inhibited these responses with similar efficacy. Collectively, these results indicate that the signal transduction pathway initiated by PDGF leading to PKC translocation in U-1242 MG cells is intact, and this pathway is inhibited by several gangliosides.

Polyamines found in gingival fluid enhance the secretory and oxidative function of human polymorphonuclear leukocytes in vitro

Many bacterial and host cells contain large amounts of polyamines that can be released at infection sites as a result of cell lysis. Consequently, the putrescine and spermidine content of gingival fluid from inflamed periodontal pockets (0.1 to 1 mM) is sharply elevated in comparison to peripheral blood. At these levels, polyamines potentiated fMet-Leu-Phe-induced Ca2+ signaling in polymorphonuclear leukocytes (PMNs) in vitro. Consistent with the essential role of Ca2+ signaling in PMN activation, secondary granule release and superoxide anion production by fMet-Leu-Phe-stimulated PMNs was enhanced in the presence of polyamines. Thus, polyamines may play a local role in modulating the antimicrobial activity of PMNs in periodontal disease.

Polyamines found in gingival fluid inhibit chemotaxis by human polymorphonuclear leukocytes in vitro

Putrescine and spermidine occur at concentrations approaching 1 mM in gingival fluid at diseased periodontal sites. Previous work demonstrates that these polyamines potentiate Ca2+ signaling in polymorphonuclear leukocytes (PMNs), resulting in enhanced degranulation and superoxide generation. The present study extends this work by characterizing the effects of polyamines on PMN chemotaxis and phagocytosis, in which Ca2+ signaling plays a less defined regulatory role. Putrescine (1 mM) and spermidine (0.1 to 0.5 mM) significantly inhibited chemotaxis to fMet-Leu-Phe and C5a (P < 0.05). This inhibition was not strongly related to any effect polyamines have on PMN adhesion, actin polymerization, or formyl peptide receptor expression. Neither putrescine nor spermidine had a significant impact on phagocytosis of opsonized bacteria by PMNs. Thus, at concentrations similar to those found in gingival fluid, polyamines could potentially inhibit recruitment of PMNs to diseased pockets without impairing their ability to engulf invading bacteria.

An inhibitor of polyamine biosynthesis impairs human polymorphonuclear leukocyte priming by tumor necrosis factor alpha

TNF primes polymorphonuclear leukocytes (PMNs) for enhanced oxidative and secretory activity and directly induces adhesion and IL-1 beta expression. Previous reports suggest that polyamine biosynthesis by ornithine decarboxylase (ODC) has an essential role in macrophage activation by TNF. In the current study, TNF induced rapid increases in the putrescine and spermine content of PMNs. Difluoromethylornithine (DFMO), a selective inhibitor of ODC, inhibited these increases and blunted the enhancement of superoxide generation and secondary granule release associated with priming by TNF. DFMO did not affect the expression of TNF receptors or block receptor-independent activation of the respiratory burst by phorbol esters. Moreover, DFMO did not antagonize induction of adhesion or IL-1 beta mRNA expression by TNF. Thus, polyamine biosynthesis plays an important role in priming by TNF, but is not involved in all PMN responses to this cytokine. This suggests that ODC is a potential target for selective chemotherapeutic modulation of the inflammatory response.

Ethics decision-making in Australian hospitals

OBJECTIVE

To describe the methods used to resolve ethical issues in hospitals throughout Australia.

DESIGN

A descriptive study from data collected by a questionnaire survey of Australian public and private hospitals.

PARTICIPANTS

Hospital administrators and employees nominated by hospital administrators.

RESULTS

Completed questionnaires were received from 739 (74%) hospitals. Methods used to resolve ethical issues included personal reflection, discussion between health professionals and discussion between health professionals and patients. A variety of committees were identified as having some role in the discussion of ethical issues, but only a small number of hospitals had established ethics committees.

CONCLUSION

Doctor-patient interaction and discussion between practitioners are the most common methods used to resolve ethical issues. Various committees are also used and, of these, ethics committees are not the most commonly consulted.

Signal transduction mechanisms in mesenchymal cells

Mesenchymal cells are continually stimulated by a wide spectrum of biological mediators. These mediators bind to receptors on the cell surface and initiate a cascade of signaling events. The initial signal transduction pathways known to be stimulated in mesenchymal cells included phospholipase C, phospholipase D, phospholipase A2, adenylate cyclase, receptor tyrosine kinases, and receptor serine/threonine kinases. These pathways are reviewed and specific applications for therapeutic intervention in wound healing and regenerative therapy in the periodontium are discussed.

Polyamine transport in human promyelocytic leukemia cells and polymorphonuclear leukocytes

We examined the kinetics of polyamine uptake by human myeloid cells at different stages of maturity. The Km values of putrescine, spermidine and spermine transport by HL-60 cells were 52, 7.9 and 8.1 microM, respectively. These values decreased to 5.1, 1.7 and 0.77 microM, respectively, in HL-60 cells induced to mature past the promyelocyte stage by DMSO. In human PMNs, the respective Km values were 501, 479 and 381 microM. Transport by HL-60 cells was enhanced when intracellular polyamine levels were reduced with difluoromethylornithine. Thus, HL-60 cell maturation is accompanied by an increase in the affinity of their polyamine transport system. This system is much more efficient than that found in end-stage PMNs, suggesting that it plays a more important role in supporting the metabolic requirements of HL-60 cells. Alternatively, the low affinity of the PMN polyamine transport system could represent an adaptation to the high polyamine concentrations found at infection sites.

Ethical issues in Australian hospitals

OBJECTIVE

To identify the most common ethical issues of concern in Australian hospitals.

DESIGN

A descriptive study using data collected by means of a questionnaire.

PARTICIPANTS

Seven hundred and thirty-nine (74%) hospital administrators and employees nominated by hospital administrators in Australian public and private hospitals.

RESULTS

Over half the respondents reported that ethical concerns had been raised in relation to: making "not for resuscitation orders"; the treatment of patients with HIV and AIDS; interprofessional conflict; and the allocation of resources.

CONCLUSION

"End of life" concerns, patient autonomy issues, questions of resource distribution, and communication difficulties commonly raise ethical concerns in Australian hospitals.

The relationship of gingival fluid leukocyte elastase activity to gingival fluid flow rate

Recent studies have suggested that leukocyte elastase activity (EA) in tissue exudates is an indicator of inflammatory disease. We assayed gingival fluid (GF) EA with a selective peptide substrate and compared it to GF flow rate with regard to its ability to detect differences in the clinical status of existing inflammatory periodontal disease in 56 human subjects. Compared to healthy sites (Gingival Index = 0, 1 to 3 mm) and mild gingivitis sites (GI = 1, 2 to 5 mm), mean GF EA was significantly (P < 0.05) higher at periodontitis sites with deep probing depths (GI = 2, 6 to 9 mm depth), but not at periodontitis sites with intermediate probing depths (GI = 2, 4 to 5 mm). When expressed as specific EA (i.e., normalized to GF protein content), mean EA was also significantly higher at deep periodontitis sites compared to healthy sites and mild gingivitis sites. In addition, specific EA was significantly higher at periodontitis sites with intermediate probing depths than at healthy sites. As predicted by previous studies, these significant increases in specific EA were associated with significant increases in mean GF flow rate. In contrast to specific EA, however, mean GF flow rate was significantly higher at gingivitis sites than at healthy sites. A strong correlation was observed between GF flow rate and specific EA (rs = 0.737, P = 0.0006). Thus, GF flow rate and GF EA appear to be related indicators of inflammation, but GF flow rate may be more sensitive to early inflammatory changes leading to mild gingivitis.

Polyamines enhance calcium mobilization in fMet-Leu-Phe-stimulated phagocytes

Spermidine and putrescine (50 microM-1 mM), found in exudates from infection sites, significantly enhance fMet-Leu-Phe-induced Ca2+ mobilization in differentiated HL-60 cells and polymorphonuclear leukocytes (PMNs) by delaying the return to basal cytosolic Ca2+ levels. This enhancement by polyamines is associated with inhibition of Ca2+ efflux across the plasma membrane. In parallel with their effects on Ca2+ signaling, polyamines also significantly prolong the kinetics of fMet-Leu-Phe-induced protein kinase C translocation. Thus, polyamines may play a novel role in modulating regulatory events in phagocytes.

A continuous fluorescence assay for protein kinase C

A 6-acryloyl-2-dimethylaminonapthalene (acrylodan)-labeled 25-amino acid peptide (acrylodan-CKK-KKRFSFKKSFKLSGFSFKKNKK-COO-), containing the protein kinase C (PKC) phosphorylation sites of brain myristoylated alanine-rich kinase C substrate protein, undergoes a 20% fluorescence decrease when it is phosphorylated by phospholipid/calcium-dependent protein kinase (PKC). This fluorescence decrease is dependent on the presence of PKC, calcium (half-maximal stimulation at pCa = 6.2), phosphatidylserine, diacylglycerol, or phorbol-12-myristate-13-acetate (half-maximal stimulation at 2 nM) and ATP, and correlates well (r = 0.997) with [32P]phosphate incorporation into the peptide. This fluorescence assay allows detection of 0.02 nM PKC, while similar concentrations of cyclic AMP-dependent or type II calmodulin-dependent protein kinases produced no change in peptide fluorescence. The method can be used to assay purified PKC as well as activity in crude brain homogenates. Incubation of PKC with staurosporine inhibits the fluorescence decrease with an IC50 of 2 nM. Thus the fluorescence decrease that occurs in the acrylodan-peptide provides a continuous fluorescence assay for PKC activity.

Phosphorylation-dependent binding of a synthetic MARCKS peptide to calmodulin

A 25-amino acid peptide, containing the four protein kinase C (PKC) phosphorylation sites and the calmodulin (CaM) binding domain of the myristoylated alanine-rich C kinase substrate (MARCKS) protein, has been synthesized and used to determine the effects of phosphorylation on its binding and regulation of CaM. PKC phosphorylation of this peptide (3.0 mol of Pi/mol of peptide) produced a 200-fold decrease in its affinity for CaM. PKC phosphorylation of the peptide resulted in its dissociation from CaM over a time course that paralleled the phosphorylation of 1 mol of serine/mol of peptide. The peptide inhibited CaM's binding to myosin light chain kinase and CaM's stimulation of phosphodiesterase and calcineurin. PKC phosphorylation of the peptide resulted in a rapid release of bound CaM, allowing its subsequent binding to myosin light chain kinase (t1/2 = 1.6 min), stimulation of phosphodiesterase (t1/2 = 1.2 min) and calcineurin (t1/2 = 1.7 min). Partially purified MARCKS protein produced a similar inhibition of CaM-phosphodiesterase which was reversed by PKC phosphorylation. PKC phosphorylation of the peptide occurred primarily at serine 8 and serine 12, and phosphorylation of serine 12 regulated peptide affinity for CaM. Thus, PKC phosphorylation of the peptide and the MARCKS protein results in the rapid release of CaM and the subsequent activation of CaM-dependent enzymes. This process might allow for interplay between PKC and CaM-dependent signal transduction pathways.

Terbium as a luminescent probe of metal-binding sites in protein kinase C

In the present report, we demonstrate that Tb3+ binds to protein kinase C and serves as a luminescent reporter of certain cationic metal-binding sites. Tb3+ titration of 50 nM protein kinase C results in a 20-fold enhancement of Tb3+ luminescence which is half-maximal at 12 microM Tb3+. A Kd of approximately 145 nM was determined for Tb3+ binding to the enzyme. The excitation spectrum of bound Tb3+ exhibits a peak at 280 nm characteristic of energy transfer from protein tryptophan or tyrosine residues. The luminescence of this complex can be markedly decreased by other metals, including Pb2+ (IC50 = 25 microM), La3+ (IC50 = 50 microM), Hg2+ (IC50 = 300 microM), Ca2+ (IC50 = 6 mM), and Zn2+ (IC50 greater than 10 mM), and chelation of Tb3+ by 2 mM EGTA. Tb3+ binding to protein kinase C is correlated with its inhibition of protein kinase activity (IC50 = 8 microM), r = 0.99) and phorbol ester binding (IC50 = 15 microM, r = 0.98). Tb3+ inhibition of protein kinase C activity cannot be overcome by excess Ca2+, but can be partially overcome with excess phosphatidylserine or by chelation of Tb3+ with EGTA. Tb3+ noncompetitively inhibits phorbol ester binding by decreasing the maximal extent of binding without significantly altering binding affinity. The results suggest that the Tb3(+)-binding site is at or allosterically related to the enzyme's phosphatidylserine-binding site, but is distinct from the phorbol ester-binding domain and the Ca2(+)-binding site that regulates enzyme activity.

Ganglioside modulation of cyclic AMP-dependent protein kinase and cyclic nucleotide phosphodiesterase in vitro

Purified cyclic AMP-dependent protein kinase (cAK) catalytic subunit phosphorylated 180-, 49-, 31-, 19-, and 14-kilodalton (kDa) proteins of rabbit sciatic nerve membranes. The ability of cAK to phosphorylate these membrane substrate proteins was inhibited by gangliosides GM1, GD1a, and GT1b with half-maximal inhibitory concentration (I50) = 7-25 microM. Neutral glycolipids and lysophosphatidylcholine were much less effective. Cyclic AMP (cAMP) kinase phosphorylation of histone IIA was inhibited by GM1, GD1a, and GT1b (I50 = 115 microM, 75 microM, and 75 microM, respectively). Inhibition by GM1 was competitive with respect to histone (Ki = 108 microM). Autophosphorylation of cAMP kinase was inhibited by GM1 (I50 = 15 microM). GT1b, GD1a, and GM1 half-maximally stimulated calmodulin-dependent cyclic nucleotide phosphodiesterase at 0.1 microM, 0.2 microM, and 0.3 microM, respectively. Although GT1b stimulated phosphodiesterase by increasing Vmax and decreasing Km (similar to calmodulin), GD1a and GM1 produced only an increase in Vmax. These results suggest that ganglioside can modulate the activity of cAMP kinase by both direct inhibition of the enzyme and indirect reduction of cAMP levels through activation of phosphodiesterase. Through these mechanisms, gangliosides may alter cAMP-dependent protein phosphorylation and cell function within the nervous system.

Relationship of human gingival crevicular fluid polyamine concentration to the percentage of spirochaetes in subgingival dental plaque

This relationship was examined at 45 inflamed periodontitis sites in 28 patients. A statistically significant positive correlation between polyamine concentration and spirochaetes was observed overall (r = 0.551, p = 0.0001). Within subgroups of this population (n = 15 each), there was no such relationship among midly inflamed sites with 5-6 mm probing depths (r = 0.0003, p = 0.999), but significant relationships among moderately inflamed sites with 5-6 mm depths (r = 0.567, p = 0.027) and 7-11 mm depths (r = 0.639, p = 0.010). Thus polyamines may be involved in subgingival plaque homeostasis at moderately inflamed periodontal sites.

Inhibition of cyclic nucleotide phosphodiesterase and calcineurin by spermine, a calcium-independent calmodulin antagonist

Spermine binding to calmodulin and its effects on two calmodulin-dependent enzymes were studied. Spermine bound to dansylated calmodulin with an apparent Ki of 0.7 mM, and to native calmodulin with a Kd of 1.1 mM in equilibrium dialysis experiments. Its binding was found to be independent of calcium. Spermine inhibited calmodulin-activated cyclic nucleotide phosphodiesterase noncompetitively with respect to calcium (Ki = 1.1 mM). Calmodulin activation of calcineurin was inhibited at similar concentrations (Ki = 1.2 mM). Spermine had little effect on basal phosphodiesterase activity or nickel-activated calcineurin activity. Inhibition of both enzymes correlated well with spermine binding to dansylcalmodulin. These findings suggest that spermine might modulate calcium-dependent events in the cell by inactivation of calmodulin via a novel calcium-independent mechanism.

Activation of cyclic nucleotide phosphodiesterase by a monosaccharide precursor of Escherichia coli lipid A

The E. coli lipid A precursor lipid X (N2,O3-diacylglucosamine 1-phosphate) activates calmodulin-dependent cyclic nucleotide phosphodiesterase in a noncooperative, calcium-independent manner by increasing its Vmax and decreasing its Km for substrate. The glycolipid produces half-maximal activation at 11 micrograms/ml and does not further enhance activation by calcium-calmodulin. Lipid X activation of phosphodiesterase requires the presence of the O3-linked hydroxymyristoyl residue. These findings suggest that lipid X could produce some of its biological effects by modulating intracellular cAMP levels.

A continuous fluorescence assay for cyclic nucleotide phosphodiesterase hydrolysis of cyclic GMP

The fluorescent 2'-methylanthraniloyl derivative of cyclic GMP undergoes a 45% decrease in fluorescence when it is cleaved by brain phosphodiesterase in the presence of calmodulin. This fluorescence decrease is dependent upon calcium, calmodulin, and phosphodiesterase, and correlates well (r = 0.996) with the disappearance of substrate as monitored by high-performance liquid chromatography. The Kd values determined by this fluorescence method and HPLC suggest that cyclic GMP and its fluorescent derivative exhibit similar kinetic parameters in their hydrolysis.

Measurement of environmental warmth in SI units

Ellis, F. P., Smith, F. E., and Walters, J. D. (1972).Brit. J. industr. Med.,29, 361-377. Measurement of environmental warmth in SI units. Although `Environmental Warmth and Its Measurement' (Medical Research Council War Memorandum No. 17), written over 25 years ago for the Royal Navy, is still widely used and has not been revised, the validation and amplification of the methods proposed by the late Dr. Thomas Bedford have in the meantime been in hand continuously in the laboratory and in the Fleet under the auspices of the Council's Royal Naval Personnel Research Committee. While it was not considered appropriate by Council to replace or to rewrite the Memorandum at the present time, in view of the recent adoption of the metric system and the units of the International System (SI Units) it was thought that it would be helpful to publish metricated charts corresponding to those which appear in the Supplement to War Memorandum No. 17, together with two additional charts which are the result of work in the post-war years, to provide investigators with simple aids for use in the laboratory or the field and to provide a basis for considering the requirements for further research.

A field assessment of a prototype meter for measuring the wet-bulb globe-thermometer index

A prototype electronic instrument for the direct measurement of the wet-bulb globe-thermometer index is described. An assessment is made of its accuracy, as compared with W.B.G.T. indices calculated from conventional thermometric data, and a comparison is made between W.B.G.T. values read from the meter and effective or corrected effective temperatures derived from separate thermometric and air velocity recording instruments in the same climates. The instrument proved to be reliable and accurate over a wide range of climates and is a useful self-contained device for use in habitability surveys and similar investigations.