Degradation of spent craft brewer's yeast by caprine rumen hyper ammonia-producing bacteria.

UNLABELLED: Spent yeast from craft beers often includes more hops (Humulus lupulus L.) secondary metabolites than traditional recipes. These compounds include α- and ß- acids, which are antimicrobial to the rumen hyper ammonia-producing bacteria (HAB) that are major contributors to amino acid degradation. The objective was to determine if the hops acids in spent craft brewer's yeast (CY; ~ 3·5 mg g(-1) hops acids) would protect it from degradation by caprine rumen bacteria and HAB when compared to a baker's yeast (BY; no hops acids). Cell suspensions were prepared by harvesting rumen fluid from fistulated goats, straining and differential centrifugation. The cells were re-suspended in media with BY or CY. After 24 h (39°C), HAB were enumerated and ammonia was measured. Fewer HAB and less ammonia was produced from CY than from BY. Pure culture experiments were conducted with Peptostreptococcus anaerobiusBG1 (caprine HAB). Ammonia production by BG1 from BY was greater than from CY. Ammonia production was greater when exogenous amino acids were included, but similar inhibition was observed in CY treatments. These results indicate that rumen micro-organisms deaminated the amino acids in CY to a lesser degree than BY. SIGNIFICANCE AND IMPACT OF THE STUDY: Spent brewer's yeast has long been included in ruminant diets as a protein supplement. However, modern craft beers often include more hops (Humulus lupulus L.) than traditional recipes. These compounds include α- and ß- acids, which are antimicrobial to the rumen hyper ammonia-producing bacteria (HAB) that are major contributors to amino acid degradation. This study demonstrated that hops acids in spent craft brewer's yeast protected protein from destruction by HABin vitro. These results suggest that the spent yeast from craft breweries, a source of beneficial hops secondary metabolites, could have value as rumen-protected protein.

Thymol and related alkyl phenols activate the hTRPA1 channel.

BACKGROUND AND PURPOSE: Thymol, a major component of thyme and oregano, has medical uses in oral care products as an astringent and antibiotic. Its distinctive sharp odour and pungent flavour are considered aversive properties. The molecular basis of these aversive properties is not well understood. EXPERIMENTAL APPROACH: The ability of thymol to activate human transient receptor potential channel A1 (hTRPA1) expressed in stably transfected human embryonic kidney 293 (HEK293) cells was measured by membrane potential and calcium-sensitive dyes in a fluorescence-imaging plate reader (FLIPR) assay. Direct activation of hTRPA1 currents was measured by whole-cell voltage clamp recording. Intracellular calcium changes were measured using fura-2 dye. The FLIPR assay was also used to measure membrane potential changes elicited by thymol after pretreatment with camphor, a known TRPA1 inhibitor. The ability of related alkyl phenols to activate hTRPA1 was also determined. KEY RESULTS: Thymol potently activated a membrane potential response and intracellular calcium increase in hTRPA1-expressing HEK293 cells in a concentration-dependent manner. Activation by thymol desensitized hTRPA1 to further exposure to thymol or the known ligand allyl isothiocyanate (AITC). The related phenols 2-tert-butyl-5-methylphenol, 2,6-diisopropylphenol (propofol) and carvacrol also activated hTRPA1. Phenols with less bulky carbon substitutions and lower logP values were less potent in general. The response to thymol was blocked by camphor. CONCLUSIONS AND IMPLICATIONS: These results suggest a role for hTRPA1 activation in the reported pungent and aversive properties of some of these pharmaceutically important phenols.

Volumetric contraction in some tooth-coloured restorative materials.

BACKGROUND: Much of the concern about the setting contraction of tooth-coloured restorative materials has been focused on the composite resins. This study investigated setting contraction of a range of glassionomer materials and included, for comparison, products from other groups of restorative materials. METHODS: A deflecting disk method was used to determine the volumetric contraction of three conventional (non-light cured) glass-ionomer cements (GICs), two restorative, one "lining" consistency and one adhesive/lining consistency resin-modified glass-ionomers (RMGIs), two resin adhesives, three restorative composite resins and two compomers. The influence of powder:liquid ratio on two hand-mixed materials was also examined. RESULTS: The light-cured materials (including RMGIs) showed substantially greater per cent contraction at 5 minutes than did the three conventional GICs (not light cured) and a substantially greater proportion of the 30-minute contraction had occurred at 5 minutes for these light-cured materials. Their further contraction after 1 hour was generally less than 5 per cent of the 1 hour contraction. CONCLUSION: Although the conventional GICs contract more slowly in the first 5 minutes, by 30 minutes the current restorative GICs and RMGIs exhibit a volumetric setting contraction that is comparable with the composite resins and compomers and is generally in the range of 2-3 per cent.

Antiallergy agents. 1. Substituted 1,8-naphthyridin-2(1H)-ones as inhibitors of SRS-A release.

A novel class of antiallergy agents, the substituted 1,8-naphthyridin-2(1H)-ones, is described. The present compounds are orally active, potent inhibitors of allergic and nonallergic bronchospasm in animal models. Structure-activity studies of the lead compound in this series, 1-phenyl-3-n-butyl-4-hydroxynaphthyridin-2(1H)-one (11), identified three compounds of interest, 1-phenyl-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1H)-one (12), 1-(3'-chlorophenyl)-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1H )-one (87), and 1-(3'-methoxyphenyl)-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1 H)-one (89). The mechanism of antiallergy activity may involve inhibition of the release of the sulfidopeptide leukotrienes. 1-Phenyl-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1H)-one, Sch 33303 (12), was selected for preclinical development as an antiallergy agent.

Substituted 1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-ones as potential antiinflammatory agents.

A series of analogues based on the 1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one ring system have been synthesized and shown to possess oral antiinflammatory activity in both the reverse passive Arthus reaction (RPAR) pleural cavity assay in rats and in the adjuvant-induced arthritic rat model (AAR). Several members of this series additionally exhibit an inhibitory effect on the in vivo production of prostaglandin- and leukotriene-derived products or arachidonic acid metabolism although these compounds exhibit no significant inhibitory activity against the cyclooxygenase and 5-lipoxygenase enzymes in vitro. Structure-activity relationships in this series are discussed.

Augmentation of leukotriene C4 and D4 release due to severe stenosis in the canine coronary artery stimulated by the calcium ionophore A23187.

In dogs undergoing 24- or 72-hr severe narrowing of the left anterior descending coronary artery (LAD), the in vitro formation of immunoreactive leukotriene C4 (LTC4) by the stenosed LAD was greatly augmented by 1 microM A23187 in a 10-min incubation at 37 degrees. This stimulated LTC4 formation was abolished by 30 microM nordihydroguaiaretic acid (NDGA). The incubation products were identified by high performance liquid chromatography and radioimmunoassay to be largely composed of LTC4 and LTD4 in similar proportion. In contrast to the stenosed LAD, the non-stenotic left circumflex coronary artery, apex of the heart, and renal artery of the same experimental animals failed to respond to the calcium ionophore up to 10 microM. The vascular and cardiac tissues from sham-operated animals also remained quiescent in the presence of A23187. The normal coronary artery showed low levels of leukotriene formation and was resistant to the ionophore. It is proposed that a latent portion of leukotriene synthesis, which can be triggered by the calcium ionophore, may play a significant role in the pathogenesis of coronary artery spasm associated with acute myocardial infarction and angina pectoris in patients with obstructive coronary artery disease.

Regulation of leukocyte and platelet lipoxygenases by hydroxyeicosanoids.

During allergic and inflammatory reactions, arachidonic acid is oxidized by lipoxygenases to a variety of biologically active products, including leukotrienes. The mechanisms for regulation of the different lipoxygenase activities are not well defined. We report here that [14C]arachidonic acid metabolism by the 5- and 15-lipoxygenase activities in rabbit leukocytes and the 12-lipoxygenase in rabbit platelets is inhibited by various hydroxyeicosatetraenoic acids (HETEs). 15-HETE was the most effective inhibitor of the 5- and 12-lipoxygenases, whereas similar inhibitory potencies were observed for 5-HETE and 12-HETE acting on the 15-lipoxygenase. These three enzyme pathways were all least sensitive to their own products HETEs. To determine which structural characteristics of 15-HETE are essential for inhibition of the 5-lipoxygenase, various derivatives were prepared and purified by high pressure liquid chromatography, and their structures were confirmed by gas chromatography-mass spectrometry. The inhibitory potencies of 15-HETE analogs with different degrees of unsaturation were in the order of three double bonds greater than 4 greater than 2 greater than 0. 15-Hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) was four times more potent than 15-HETE. The 15-acetoxy, 15-keto and methyl ester derivatives were of comparable activity to 15-HETE, and the 15-acetoxy methyl ester derivative was less potent. Based upon the observed patterns of inhibition, we postulate that complex interregulatory relationships exist between the various lipoxygenases, and that cells containing these lipoxygenases may interact with each other via their lipoxygenase metabolites.

Standardizing evaluations of the clinical marginal fracture of amalgam.

In this study, we investigated both inter-examiner and intra-examiner differences in the evaluation of the marginal fracture characteristics of dental amalgam restorations. Evaluations were made by matching intra-oral photographs of the occlusal surfaces of clinical restorations to a reference set of clinical photographs illustrating increasing amounts of marginal fracture. Four amalgam alloys and five examiners provided the data base. Differences in marginal fracture indices were found among examiners and between evaluation times for the same examiners. However, these differences were reduced significantly after application of a standardization procedure.

Calcium ionophore and chemotactic peptide stimulation of peptidoleukotriene synthesis in DMSO-differentiated HL60 cells.

The human promyelocytic leukemia cell line HL60 can be differentiated to mature granulocytes upon exposure to DMSO (1.3%, 6 days). The ability of these cells to metabolize arachidonic acid via the 5-lipoxygenase pathway to form 5-HETE, LTB4, and 5,12-diHETEs, has been previously documented. However, the production of peptidoleukotrienes by DMSO-differentiated HL60 cells has not been previously reported. Arachidonic acid metabolites produced via 5-lipoxygenase were identified by reverse-phase, high-performance liquid chromatography, immunoreactivity specific for peptidoleukotriene, glutamyl transpeptidase transformation, characteristic UV spectra, and GC mass spectra. Leukotriene synthesis in the DMSO-differentiated HL60 cell is maximal at 5 min when stimulated with the calcium ioniphore, A23187 (1 microM), in the presence of calcium. These cells produce 12.94 +/- 1.8 ng/10(6) cells of LTC4 and 3.8 +/- 0.4 ng/10(6) cells of LTB4. LTC4 and LTB4 are also synthesized in the undifferentiated cell when stimulated with 1 microM A23187 and 1 mM Ca2+, but in much smaller quantities, i.e., 1.91 +/- 0.42 ng/10(6) cells of LTC4 and 0.41 ng +/- 0.06/10(6) cells of LTB4. The synthetic chemotactic peptide, f-Met-Leu-Phe, also elicits formation of LTC4 and LTB4 in a dose-dependent manner in the presence of exogenously added calcium. Maximal stimulation of DMSO-differentiated cells with f-Met-Leu-Phe produces 2.5 +/- 0.2 ng of LTC4 and 1.45 +/- 0.2 ng of LTB4 per 10(6) cells. The observation that DMSO-differentiated HL60 cells produce LTC4, as well as other 5-lipoxygenase products, increases the utility of this cell line for unraveling the regulation of leukotriene biosynthesis by granulocytes.

Apparatus for precision calibration of skinfold calipers.

Despite the fact that skinfold calipers are widely used to measure subcutaneous adipose tissue, the current methods of calibration are quite crude. Methods such as hanging masses from the caliper jaws until they remain open, lack validity and reliability because the caliper jaws are stationary instead of dynamic, and the opening jaws give an upscale reading of the jaw gap not a downscale reading that occurs when the calipers are being used to measure skinfolds. This report describes how to build an apparatus capable of measuring static and dynamic, upscale and downscale jaw pressures of a variety of caliper types and also provides guidelines specifically for calibration and servicing of Harpenden calipers. The key areas to maintain are the caliper springs (which should have spring coefficients ranging 1.104-1.153 N.mm-1 ), the pivot joint (which should operate smoothly), the indicator mechanism (which should require only 0.78-0.88 N for full movement), and the jaw alignment which should be square to ensure that the full effective jaw surface area of 90 mm2 is applied to the skinfold. While there are insufficient data at this time to prescribe rigid calibration criteria, assessment of approximately 100 new and used Harpenden calipers indicates that, after servicing, the important dynamic downscale jaw pressure will range 7.7-8.4 g.mm-2 at 5 mm of jaw gap and 7.3-8.0 g.mm-2 at 40 mm of jaw gap. Dynamic upscale jaw pressure should be within 1.0-1.5 g.mm-2 of the corresponding dynamic downscale jaw pressure. Am. J. Hum. Biol. 10:689-697, 1998. © 1998 Wiley-Liss, Inc.

Synthesis and characterization of [1-(13)C]-and d8-arachidonic acid.

Methyld 8- and [1-(13)C] 5,8,11,14-eicosatetraenoate (arachidonate) were prepared from a common synthetic precursor, 4,7,10,13-nonadecatetrayn-1-ol. The purified products were characterized by gas chromatography-mass spectrometry. Mass spectra oft-butyldimethylsilyl esters ofd 8-and [1-(13)C]-arachidonic acid showed a most intense [M-57](+) peak at high mass. The isotopic purity of methyl [1-(13)C] arachidonate was 99% and that of methyld 8-arachidonate was 56%. Whend 8-arachidonic acid was prepared by direct deuteration of 5,8,11,14-eicosatetraynoic acid, the isotopic purity of the sample was 86%.

Comparison of three standards for quantifying occlusal loss of composite restorations.

Occlusal loss of resin composite in posterior restorations may be measured by assessing the exposure of cavity walls. The purpose of this study was to compare three standard scales used to quantify occlusal loss on stone replicas of posterior composites. Measurements of occlusal loss, on 60 stone replicas selected from two clinical studies, were obtained by comparison with three standard scales: L-calibrated die stone standards derived from clinical restorations (Leinfelder), M-dies with cylindrical incremental defects (M-L scale), and V-tooth-sized dies with restoration-like incremental defects (Vivadent). Evaluators with different dental and evaluating experience carried out the assessment using each standard on two different occasions. Differences among results obtained using the three standard scales were comparatively small when assessments were carried out by experienced evaluators. Use of the V standard consistently achieved a higher level of agreement by pairs of evaluators.

The finishing and early marginal fracture of clinical amalgam restorations.

One operator placed 249 Tytin amalgam restorations in Class I and II preparations in the permanent teeth of 60 patients each of whom received a minimum of three restorations. At least one of these restorations was carved-only, at least one was immediately finished (at 8 or 10 min after trituration), and at least one restoration was polished (more than 24 h after placement). Restorations were principally assessed for marginal fracture at baseline and 1 year using the 11-unit scale for the evaluation of photographs developed by Mahler. Five factors were also assessed clinically at 1 year. Amalgam restorations, polished using finishing burs and rubber points at least 24 h after placement, exhibited more initial marginal fracture than carved-only or immediately finished restorations. At 1 year, the three techniques were comparable except for the superior surface texture of the polished restorations. The technique of immediate finishing of amalgam restorations has nothing to commend it in preference to existing techniques.

Finishing of amalgam restorations: a three-year clinical study.

Class I and Class II amalgam restorations were placed in the permanent teeth of 66 patients, each of whom received a minimum of three restorations. At least one of these restorations was carved-only, at least one was immediately finished (using a prophylaxis paste on rubber cups at low speed, 8 or 10 min after trituration), and at least one restoration was polished (using finishing burs and polishing points, more than 24 h after placement). The number of restorations available for assessment of marginal fracture using the 11-unit photographic scale developed by Mahler was 253 at baseline, 249 at 1-year and 2-year recalls and 228 at the 3-year recall. Although polished restorations exhibited greater initial (baseline) marginal fracture, at 1-year, 2-year and 3-year recalls the restorations were found to exhibit a similar amount of marginal fracture regardless of the finishing technique. The amount of perceived marginal fracture increased steadily after 1 year. The immediate finishing of amalgam restorations showed no long-term benefit over the other techniques and has little to commend it. The clinical finishing of amalgam restorations is discussed in the light of this and other research.

A clinical evaluation of posterior composite resin restorations: 8-year findings.

OBJECTIVES: From a continuing investigation of the clinical performance of three different types of composite resin, the findings of the clinical evaluation at 8 years are presented. METHODS: One operator placed 330 restorations in Class I and Class II preparations in the posterior teeth of 72 patients. Every patient received at least one restoration of each type of material: a microfilled composite, a small particle hybrid, a relatively coarse particle hybrid, and an amalgam control. Restorations were evaluated using clinical criteria. RESULTS: Forty six patients attended the 8-year recall. Twenty-five of the 213 restorations (13.7% of the composites and 5.8% of the amalgams) originally placed in these 46 patients had previously failed or been lost from the study or were assessed as requiring replacement at the 8-year recall. Bulk fracture and secondary caries at the margin were the most common forms of failure in the composite restorations. Other failures or losses were associated with a non-margin defect in the composite, caries not associated with the restoration, pulpal considerations, extraction for orthodontics and reasons unknown. One-hundred and ninety-three restorations (including five that required replacement) were available for clinical evaluation at 8 years and these included 17 Class II restorations. Significantly fewer restorations placed with the coarse particle hybrid exhibited evidence of marginal deterioration. CONCLUSION: At 8 years, composite restorations in posterior teeth had failed at a rate two to three times that of amalgam restorations. The most common types of failure were bulk fracture and secondary caries at the margin.

Microleakage of amalgam alloys: an update.

Using an in vitro air pressure test, the authors found a wide variation in the microleakage characteristics of amalgam restorations made from 33 recently manufactured precapsulated alloys. Spherical particle alloys as a group exhibited the highest microleakage values. When the authors changed the mercury/alloy ratios to produce 1 percent more mercury in the capsules by weight, microleakage decreased significantly. Because extensive microleakage of amalgam restorations has been related to increased postoperative sensitivity, the authors suggest that practitioners should be alert to this potential problem.

Occlusal margin defects around different types of composite resin restorations in posterior teeth.

Using stone replicas of individual restorations from a clinical study investigating three types of posterior composite resins, four types of defects were identified on the occlusal margins. It was observed that particular types of defects were commonly associated with each type of composite resin. The microfilled composite usually exhibited crevice formation (marginal fracture), the small-particle hybrid showed evidence of both wear and crevice formation, and a coarse composite resin most noticeably exhibited wear. Fracture of excess composite was associated with the fine-textured composites.

Direct posterior composite resin restorations: a review. 2. Clinical technique.

Despite the increased use of composite resin to restore posterior teeth, there is evidence that clinicians should be selective in their use of these restorations. This paper describes the clinical technique--preparatory procedures, preparation of the cavity, preparation for placement of composite resin, placement of composite resin and finishing of the restoration--for the relatively conservative use of composite resin in posterior teeth and reviews the literature to discuss briefly many of the controversial aspects of the technique.

X-ray mapping of dental amalgam using the electron microprobe.

Tin, copper, silver and mercury X-ray maps were obtained for amalgams prepared from three "high copper" commercial alloys. The data obtained from quantitative analysis of a silver-copper dispersed amalgam was subjected to major element analysis. X-ray mapping was found to reflect accurately the relative quantity of an element present in different regions of a map, thereby providing a reliable qualitative, part-quantitative analysis of the structure of the amalgam.

The static creep of amalgams from fifteen alloys.

The static creep of amalgams prepared from fifteen conventional Ag3Sn and higher copper alloys was investigated one week after packing. The rate at which the different alloys develop resistance to creep was compared by testing amalgams at a number of times other than one week. A microfine lathe-cut alloy possesses the highest static creep and the single melt high copper type of alloy the lowest. An admixed high copper group of alloys possesses static creep similar to the silver-copper dispersed alloys. The rate at which amalgam develops a resistance to creep is dependent on the alloy type.