Effect of sterilization on the strength and cutting efficiency of twist drills

Retentive-pin twist drills were subjected to four methods of sterilization and then examined to determine possible effects on resistance to fracture, cutting efficiency, and surface condition. Sterilization methods included steam autoclave, chemical vapor autoclave, dry heat, and immersion in glutaraldehyde. Although the steam and chemical vapor groups had lower mean fracture strengths after sterilization, there was no statistically significant difference among the groups. Only the steam autoclave group showed a statistically significant loss of cutting efficiency. Scanning electron microscopic evaluation revealed that only drills sterilized by steam autoclave showed changes in the surface condition or cutting edges.

gamma-Aminobutyric acid inhibition of histamine-induced inositol phosphate formation in guinea-pig cerebellum: comparison with guinea-pig and rat cerebral cortex

1. gamma-Aminobutyric acid (GABA), 2 mM, inhibited basal accumulation of [3H]-inositol monophosphate ([3H]-IP1) in lithium-treated slices of guinea-pig cerebellum preincubated with [3H]-inositol. In contrast, 2 mM GABA stimulated the accumulation of [3H]-IP1 in rat cerebral cortical slices over a 60 min incubation period, but had no significant effect in slices of guinea-pig cerebral cortex. The estimated IC50 for the inhibitory action of GABA in guinea-pig cerebellar slices was 0.52 +/- 0.12 mM. 2. GABA inhibited histamine-induced [3H]-IP1 accumulation in guinea-pig cerebellar slices in a non-competitive manner. The best-fit value for the maximum level of inhibition was 74 +/- 6%. The estimated IC50 for GABA was 0.77 +/- 0.15 mM and was not significantly different from the IC50 for inhibition of the basal accumulation of [3H]-IP1. The response to histamine in guinea-pig and rat cerebral cortical slices was also inhibited by 2 mM GABA. 3. In guinea-pig cerebellar slices 2 mM GABA potentiated histamine-induced [3H]-inositol bisphosphate ([3H]-IP2) accumulation, whereas in both guinea-pig and rat cerebral cortex the effect was inhibition. 4. Isoguvacine and muscimol, GABAA-selective agonists, and (-)-baclofen, GABA(B)-selective, had no significant effect on basal or histamine-stimulated accumulation of [3H]-IPs in guinea-pig cerebellar slices. (-)-Baclofen had only a weak inhibitory effect on [3H]-IP1 accumulation in guinea-pig-cerebral cortex (16 +/- 6% inhibition with 10 microM (-)-baclofen), whereas in rat cerebral cortex (-)-baclofen mimicked the inhibitory effect of GABA. 5. Nipecotic acid (1 mM) had qualitatively similar effects to those of 2mm GABA in guinea-pig cerebellar slices. 6. The competitive GABA uptake inhibitors SK&F 89976-A, SK&F 100330-A and SK&F 100561-A were potent histamine H,-receptor antagonists, as indicated by the inhibition of [3H]-mepyramine binding to homogenates of guinea-pig cerebellum and cerebral cortex. 7. GABA (2 mM) caused a small inhibition (12 + 3%) of [3H]-inositol incorporation into total inositol phospholipids in guinea-pig cerebellar slices, as in rat cerebral cortical slices, whereas 0.2mm histamine caused a small stimulation (15 + 4%). In the presence of both GABA and histamine, [3H]-inositol incorporation was unchanged from basal (101 + 5%). 8. GABA also inhibited [3H]-IP1 formation induced by endothelin-1 in guinea-pig cerebellar slices and increased, but not significantly, the amount of [3H]-IP2 accumulated. This, taken with the inhibitory effect on basal and histamine-stimulated accumulation, suggests that the action of GABA in guinea-pig cerebellar slices may be non-selective and may not be exerted through a specific GABA receptor.

Fracture resistance of Kevlar-reinforced poly(methyl methacrylate) resin: a preliminary study

The reinforcing effect of Kevlar fibers incorporated in processed poly(methyl methacrylate) resin samples was studied using 0% (controls), 0.5%, 1%, and 2% by weight of the added fibers. The samples were subjected to impact testing to determine fracture resistance, and sample groups were statistically compared using an ANOVA. Each reinforced sample had significantly greater fracture resistance (P less than 0.05) than the control, and no difference was found either within or between control groups. The use of reinforcing Kevlar fibers appears to enhance the fracture resistance of acrylic resin denture base materials.

Ca2(+)-dependence provides evidence for differing mechanisms of GABA-induced inositol phosphate formation and GABA potentiation of inositol phosphate formation induced by noradrenaline in rat cerebral cortex

[3H]Inositol phosphate formation ([3H]IP) induced by gamma-aminobutyric acid (GABA) in slices of rat cerebral cortex prelabelled with [3H]inositol was abolished in Krebs-Henseleit medium without added Ca2+, but could be restored by addition of Ca2+. In contrast, GABA potentiation of noradrenaline-induced [3H]IP accumulation in the same tissue was still observed in the absence of added Ca2+. This provides evidence (a) that the effect of GABA alone on [3H]IP formation is indirect and (b) that the mechanism of this effect is unlikely to be the same as for the potentiation by GABA of [3H]IP accumulation induced by noradrenaline.

Disinfection/sterilization protocols recommended by manufacturers of impression materials

A survey of six companies manufacturing 12 commonly used impression materials was conducted to determine current recommended impression disinfection techniques. Only one company provided a protocol based on studies of its own product, and only two chemical disinfectants were evaluated, with little test information provided. It was concluded that none of the six impression manufacturers had an appropriate, complete disinfectant protocol.

Potentiation by gamma-aminobutyric acid of alpha 1-agonist-induced accumulation of inositol phosphates in slices of rat cerebral cortex

Noradrenaline-induced accumulation of 3H-labeled inositol mono-, bis-, and trisphosphate (IP1, IP2, and IP3, respectively) in lithium-treated slices of rat cerebral cortex preincubated with [3H]inositol was potentiated by gamma-aminobutyric acid (GABA). However, the effect on [3H]IP2 accumulation was much greater than that on [3H]IP1 or [3H]IP3 accumulation. The principal effect of GABA on noradrenaline concentration-response curves for both [3H]IP1 and [3H]IP2 was to cause an increase in the maximal response attainable. However, whereas the EC50 for GABA potentiation of [3H]IP1 formation was 0.5 mM, the curve for the potentiation of [3H]IP2 formation showed a marked upturn at GABA concentrations of greater than 1 mM. Prazosin (1 microM) blocked the noradrenaline-induced formation of all three inositol phosphates (IPs), in both the presence and the absence of 2 mM GABA. 3H-IP formation induced by phenylephrine and methoxamine was also potentiated by GABA, and again the greatest effect was on [3H]IP2 accumulation. The ratio of [3H]IP2/[3H]IP1 formed in response to 100 microM noradrenaline was increased by 2 mM GABA at all times from 10 to 60 min, whereas the ratio of [3H]IP3/[3H]IP1 was little altered. The effect of GABA was not mimicked by the GABAA agonists isoguvacine and 3-aminopropanesulphonic acid and was not blocked by bicuculline methiodide. (-)-Baclofen, a GABAB agonist, did produce some stimulation of the response to noradrenaline, but to a much lesser extent than GABA. Of the agents tested, nipecotic acid came nearest to reproducing the effect of GABA, in that the major effect was on [3H]IP2 accumulation. The effects of 2 mM GABA and 2 mM nipecotic acid were not additive. GABA potentiation of noradrenaline-induced 3H-IP formation was still apparent in the absence of Li+, but the increase of [3H]IP2 content was less than that of [3H]IP1 content.

Characteristics of endothelin-1 and endothelin-3 stimulation of phosphoinositide breakdown differ between regions of guinea-pig and rat brain

Endothelin-3 was almost equipotent with endothelin-1 (ET-1) in stimulating phosphoinositide hydrolysis, as indicated by [3H]inositol phosphate formation, in cross-chopped slices of guinea-pig cerebellum, rat cerebellum and rat cerebral cortex. The magnitude of [3H]inositol phosphate formation was greatest in guinea-pig cerebellum, approximately 10-fold over basal levels. The similar level of [3H]IP1 accumulation produced by 1 mumol.l-1 ET-1 in rat cerebellum and cerebral cortex (circa 3-fold over basal) did not mirror the large difference in high-affinity [125I]ET-1 binding sites in the two regions. Moreover, the EC50 for ET-induced [3H]IP1 formation differed markedly between the three tissues (7 +/- 2 nmol.l-1 in rat cerebral cortex, 65 +/- 15 nmol.l-1 in guinea-pig cerebellum and greater than 200 nmol.l-1 in rat cerebellum). Only in rat cerebral cortex was the EC50 of the same order as has been reported for peripheral responses to ET-1.

Synthesis and biological evaluation of omega-(N,N,N-trialkylammonium)alkyl esters and thioesters of carboxylic acid nonsteroidal antiinflammatory agents

A series of novel omega-(N,N,N-trialkylammonium)alkyl ester and thioester derivatives [RCOM(CH2)nNR3+ X-, M = O or S. n = 2-6, X = I or Cl] of 11 nonsteroidal antiinflammatory carboxylic acid agents (naproxen, ketorolac, indomethacin, ibuprofen, sulindac, ketoprofen, flufenamic acid, mefenamic acid, zomepirac, etodolac, and tifurac) was prepared and evaluated for their antiinflammatory, analgesic, and gastrointestinal erosive properties. In general, each prodrug retained the antiinflammatory activity characteristic of the corresponding parent drug but exhibited moderately to greatly reduced gastrointestinal erosive properties and significantly reduced analgetic potencies. This profile is likely due to a combination of factors including the rate of hydrolysis of the esters in the stomach, gut, and plasma, changes in the locus of absorption of the prodrug or nonsteroidal antiinflammatory drug (NSAID), and altered metabolic disposition patterns resulting from these changes. The results obtained from the compounds of this series indicate that esters of this general class may offer a means to modulate both the aqueous/lipid solubility and the hydrolytic/enzymatic cleavage indices of NSAID prodrugs which potentially possess a more favorable therapeutic ratio of antiinflammatory to gastrointestinal erosive activities.

Synthesis and antiinflammatory and analgesic activity of 5-aroyl-6-(methylthio)-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-ca rboxyl ic acids and 1-methyl-4-(methylthio)-5-aroylpyrrole-2-acetic acids

5-Aroyl-6-(methylthio)-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carb oxylic acids and 1-methyl-4-(methylthio)-5-aroylpyrrole-2-acetic acids were synthesized and assayed as antiinflammatory and analgesic agents. The majority of these compounds exhibit a surprisingly low level of antiinflammatory activity (rat carrageenan paw) but have considerable potency as analgesics (mouse phenylquinone writing). For example, the p-tolyl-substituted bicyclic and monocyclic compounds 44 and 58 are 301 and 66 times more potent than aspirin (mouse writhing) but only 3.4 and 1.5 times more potent than phenylbutazone in the antiinflammatory screen (rat paw).

Effects of nicotine chewing gum on complete dentures and their soft-tissue-bearing areas

One hundred six edentulous subjects were given nicotine-containing chewing gum to evaluate the ability to chew the gum, to observe the adherence of the gum to denture-base materials, and to evaluate the effect of gum chewing on denture-bearing tissues. Prior to the 13-week study, the denture-bearing ridges and the tissue and polished surfaces of the denture were evaluated clinically and photographed. Questionnaires were used to elicit personal habits of the subjects. Of the 59 subjects completing the study, most could manipulate and chew the gum effectively, three-fourths reported that gum adherence was not a problem, and no adverse reaction to oral tissues was observed.

Edema and cell infiltration in the phorbol ester-treated mouse ear are temporally separate and can be differentially modulated by pharmacologic agents

The temporal patterns of edema and accumulation of the PMN marker enzyme, myeloperoxidase (MPO), were examined following application of tetradecanoylphorbol acetate (TPA) to mouse ears. After application of 2.5 micrograms TPA, edema peaked at 6 hr, while MPO activity peaked at 24 hr. Pharmacological agents with defined mechanisms of action, delivered orally or topically, were assessed for effects on these responses. For oral administration, compounds were delivered 1 hr before and 6 hr after TPA and for topical administration compounds were delivered at 15 min and 6 hr after TPA. Topical and oral corticosteroids inhibited both edema and MPO accumulation. Cyclooxygenase and lipoxygenase inhibitors were very effective against MPO accumulation but were either inactive or moderately active vs edema. Anti-histamine/anti-serotonin agents had little effect on edema, but could inhibit or exacerbate MPO accumulation depending on dose and route of administration. Topically applied histamine itself did not effect TPA-induced edema, but markedly suppressed MPO accumulation. Acetone, the vehicle, when topically applied between 0.5 and 2 hr after TPA inhibited MPO accumulation by 60-80%, but had little effect on edema. Acetone applied before 0.5 hr or after 2 hr had no effect on either parameter. These results indicate that in the TPA-induced ear inflammation model the MPO response at 24 hr may be a useful additional indicator of drug activity.

GABAB receptor-mediated inhibition of histamine H1-receptor-induced inositol phosphate formation in slices of rat cerebral cortex

Histamine-stimulated accumulation of [3H]inositol monophosphate ([3H]IP1) in lithium-treated slices of rat cerebral cortex was inhibited by gamma-aminobutyric acid (GABA) (IC50 0.30 +/- 0.03 mM). The maximum level of inhibition was 69 +/- 2%. GABA alone caused a small stimulation of basal accumulation of [3H]IP1. The inhibitory action of GABA on the response to histamine was mimicked by the GABAB agonist (-)-baclofen, IC50 0.69 +/- 0.04 microM, which was 430-fold more potent as an inhibitor than the (+)-isomer. (-)-Baclofen also inhibited histamine-induced formation of [3H]inositol bisphosphate ([3H]IP2) and [3H] inositol trisphosphate ([3H]IP3). Inhibition curves for GABA and for (-)-and and (+)-baclofen had Hill coefficients greater than unity. (-)-Baclofen, at concentrations that caused inhibition of histamine-induced [3H]IP1 accumulation, did not alter the basal level of [3H]IP1 or the incorporation of [3H]inositol into total inositol phospholipids. Isoguvacine, a GABAA agonist, had no effect on either the histamine-stimulated or basal accumulation of [3H]IP1. GABA had no effect on carbachol-stimulated [3H]IP1 formation.

Topical nonsteroidal antipsoriatic agents. 2. 2,3-(Alkylidenedioxy)naphthalene analogues of lonapalene

A series of 2,3-(alkylidenedioxy)naphthalene (5a-p) analogues of lonapalene (RS-43179, 1), a 5-lipoxygenase inhibitor currently under clinical investigation for the treatment of psoriasis, has been prepared and evaluated for topical inhibitory activity against arachidonic acid induced mouse ear edema. The results of these studies demonstrate that introduction of the fused 2,3-alkylidenedioxy ring, in place of the acyclic 2,3-dialkoxy substituent pattern characteristic of the previous series, caused a modest dimunition in overall potency within the series. These results suggest a potential steric intolerance for these extended planar analogues, in comparison with their 2,3-dialkoxy predecessors.

Digitonin-solubilized histamine H1-receptors bind to polyethylenimine-treated glass-fibre filters

The binding of [3H]mepyramine to histamine H1-receptors solublized from guinea-pig cerebellum by 1% digitonin could be assayed by adsorption of the receptor-bound [3H]ligand to glass-fibre filters pretreated with 0.3% polyethylenimine (PEI). Non-specific binding was higher than in parallel experiments in which the bound and free [3H]ligand was separated by gel-filtration on Sephadex G-25 columns, but the parameters characterizing the inhibition curves were otherwise similar. The PEI-treated filter method could also be used to assay [3H]-(+)-N-methyl-4-methyl-diphenhydramine ([3H]QMDP) binding to solubilized H1-receptors, but the level of non-specific binding was higher and was only satisfactorily defined by icotidine or temelastine. A particular utility of the PEI-treated filter assay will be in measurements of the kinetics of H1-receptor-ligand interactions.

[3H]-(+)-N-methyl-4-methyldiphenhydramine, a quaternary radioligand for the histamine H1-receptor

1. A series of derivatives of 4-methyldiphenhydramine have been examined as potential quaternary radioligands for the histamine H1-receptor. 2. [3H]-(+)-N-methyl-4-methyldiphenhydramine ([3H]-QMDP), 83 Ci mmol-1, was synthesized by methylation of the tertiary analogue and purified by high-voltage electrophoresis. 3. [3H]-QMDP bound to H1-receptors in a washed homogenate from guinea-pig cerebellum with an affinity constant, Ka, of 1.14 +/- 0.03 x 10(9) M-1. The proportion of non-specific binding of 0.3-0.6 nM [3H]-QMDP, defined by 0.4 microM mepyramine, was usually in the range 15-45%, depending on the method of measurement of binding. The affinity of [3H]-QMDP was similar in guinea-pig cerebellum, cerebral cortex and hippocampus, but was lower, 1.4 x 10(8) M-1, in rat cerebral cortex. 4. Evidence was obtained for the presence of a secondary, non-muscarinic, binding site for [3H]-QMDP in guinea-pig cerebellum, approximate Ka 1.5 x 10(7) M-1, accounting for circa 4% of the total binding of 1 nM [3H]-QMDP. 5. There was a very good correlation between the affinities of 15 compounds for the H1-receptor determined from inhibition of [3H]-QMDP binding and from inhibition of [3H]-mepyramine binding. 6. The potential utility of [3H]-QMDP for studies of H1-receptors in the plasma membrane of cells in culture is discussed.

Temperature-dependence of the kinetics of the binding of [3H]-(+)-N-methyl-4-methyldiphenhydramine to the histamine H1-receptor: comparison with the kinetics of [3H]-mepyramine

1. The dissociation of [3H]-(+)-N-methyl-4-methyldiphenhydramine ([3H]-QMDP) from the histamine H1-receptor was markedly temperature-dependent. The t1/2 was 4 min at 37 degrees C and 16 h at 6 degrees C. The association rate constant, k1, was also temperature-dependent, but not to the same extent as k-1. 2. Plots of the observed rate constant for [3H]-QMDP-receptor complex formation, kon, versus [3H-QMDP] were linear at both 30 degrees C and 10 degrees C, consistent with the interaction of [3H]-QMDP with the H1-receptor being a simple, one-step equilibrium. 3. The ratio of the kinetic constants, k1/k-1, indicated that the affinity constant of [3H]-QMDP for the H1-receptor should increase with decreasing temperature. Measurement of (+)-QMDP antagonism of the contraction of longitudinal muscle strips from guinea-pig small intestine induced by histamine at 37 degrees C, 30 degrees C and 25 degrees C provided some evidence that the affinity of (+)-QMDP is greater at 25 degrees C than 37 degrees C. However, the flattening of the concentration-response curves for histamine at low concentrations of (+)-QMDP at 30 degrees C and 25 degrees C is consistent with a slow dissociation of the (+)-QMDP-receptor complex and hence an incomplete equilibration with the agonist. 4. Arrhenius plots for k1 and k-1 for [3H]-QMDP were linear between 37 degrees C and 6 degrees C. The activation energies, Ea, for complex formation and dissociation were 77 +/- 4 and 129 +/- 3 kJ mol-1, respectively. 5. An Arrhenius plot for k-1 for the dissociation of [3H]-mepyramine from the H1-receptor was also linear between 37 degrees C and 6 degrees C. The activation energy was 140 +/- 2 kJ mol-1. 6. Activation energies for complex formation with the H1-receptor, Eaf, and complex dissociation, Ead, were similar for [3H]-QMDP and [3H]-mepyramine. The energy difference, Eaf--Ead, equivalent to the enthalpy change, did not differ significantly for the two ligands (-52 and -48 kJ mol-1, respectively). The larger values of k1 and k-1 for [3H]-mepyramine compared to [3H]-QMDP imply the presence of an entropic component in the interaction. 7. The simplest explanation for these observations is that transfer from the aqueous phase into a hydrophobic region is a significant factor in antagonist-H1-receptor interaction. This would be entropically more favourable for [3H]-mepyramine, a tertiary amine, than for [3H]-QMDP, a quaternary amine.

Persistent neonatal hyperinsulinism

Over a 3-year period, the diagnosis of persistent neonatal hyperinsulinism (PNH) was made in seven infants, from an unselected cohort of 18,726 births, all of Saudi Arabian origin. Thus the incidence of PNH was one in 2,675 births. The high incidence, associated consanguinity, and occurrence in siblings suggest that PNH may be inherited as an autosomal recessive disorder.

Utilization of an Epstein-Barr virus replicon as a eukaryotic expression vector

Epstein-Barr virus (EBV) replicons which include the genetic element oriP and a functional gene for Epstein-Barr nuclear antigen (EBNA-1) can be maintained episomally in a variety of mammalian cell lines [Yates et al., Nature 313 (1985) 812-815]. We have assessed the application of an EBV replicon for foreign gene expression. Two cDNAs, human interferon-gamma (IFN-gamma) and the extracellular domain of the human epidermal growth factor receptor (EGF-Rex), cloned in an EBV replicon, were efficiently expressed and the protein was secreted into the extracellular media. Expression in human embryonic 293 cells was approximately ten-fold higher than in CV-1 cells. The expression of the human protein is dependent upon the orientation of the IFN-gamma transcriptional cassette relative to the other genetic elements within the vector.

Intraarticular injection of Propionibacterium acnes causes an erosive arthritis in rats

Formalin killed Propionibacterium acnes, was injected intraarticularly into the stifle joint of rats. The reaction was assessed by radiologic and histologic examination. A single injection induced a marginally erosive synovitis that receded by day 30. A second injection administered in the same joint resulted in tissue destruction that was evident radiographically. Treatment by dexamethasone and some disease modifying drugs, i.e. chloroquine, hydroxychloroquine, sodium aurothiomalate and cyclophosphamide, significantly inhibited cartilage and bone erosion while nonsteroidal antiinflammatory agents had no effect.

Diphenyldisulfide inhibits indomethacin-induced ulcerogenesis in rats

Indomethacin was administered subcutaneously to rats, 4 mg/kg/day for 4 consecutive days in order to produce erosions of the small intestine which were scored at necropsy on day 5. Orally administered phenidone (up to 250 mg/kg/day), a mixed cycloocygenase-lipoxygenase inhibitor, failed to produce intestinal erosions, but tended to exacerbate indomethacin-induced erosions. A 5-LO inhibitor, diphenyldisulfide, provided significant protection at 10-100 mg/kg when given orally to indomethacin-treated rats. Sulfasalazine, auranofin and cyproheptadine, but not cimetidine, also protected, suggesting a role for mast cell activation and leukotriene generation in indomethacin-induced ulcerogenesis.

An evaluation of squamous cell carcinoma antigen in patients with cervical squamous cell carcinoma

In a prospective study, serum concentrations of squamous cell carcinoma antigen, a subfraction of tumor antigen (TA-4), were determined by radioimmunoassay from healthy donors, pregnant women, and subjects with various benign and malignant gynecologic diseases. Ninety-six percent of 99 healthy persons including all 52 female controls, the 15 pregnant patients, and all 23 subjects with benign gynecologic tumors, had squamous cell carcinoma antigen levels less than 2.0 ng/ml. Seven of 51 (14%) patients with cervical intraepithelial neoplasia and 16 of 24 (67%) patients with cervical squamous cell carcinoma had squamous cell carcinoma antigen levels greater than 2.0 ng/ml. Declining and rising levels of squamous cell carcinoma antigen, which were determined sequentially in nine cases of cervical carcinoma that were associated with elevated pretreatment levels of squamous cell carcinoma antigen, correlated with regression and progression of the disease. Serial serum levels of squamous cell carcinoma antigen provide a noninvasive means of monitoring the effects of individual therapy in patients with cervical squamous cell carcinoma.