Toxic Relationships and Arms-Race Coevolution Revisited.

Toxin evolution in animals is one of the most fascinating and complex subjects of scientific inquiry today. Gaining an understanding of toxins poses a multifaceted challenge given the diverse modes of acquisition, evolutionary adaptations, and abiotic components that affect toxin phenotypes. Here, we highlight some of the main genetic and ecological factors that influence toxin evolution and discuss the role of antagonistic interactions and coevolutionary dynamics in shaping the direction and extent of toxicity and resistance in animals. We focus on toxic Pacific newts (family Salamandridae, genus Taricha) as a system to investigate and better evaluate the widely distributed toxin they possess, tetrodotoxin (TTX), and the hypothesized model of arms-race coevolution with snake predators that is used to explain phenotypic patterns of newt toxicity. Finally, we propose an alternative coevolutionary model that incorporates TTX-producing bacteria and draws from an elicitor-receptor concept to explain TTX evolution and ecology.

Failure to detect human T-lymphotropic virus antibody in wild-caught New World primates.

We conducted a study to look for a simian counterpart of human T-lymphotropic virus (HTLV) in wild-caught monkeys in the Republic of Panama. Serum specimens were obtained from 102 monkeys (Ateles fusciceps, n = 75; Alouatta villosa, n = 18; and Cebus capucinus, n = 9) captured in Panama's Darien rain forest in 1979-1980. Specimens were screened for HTLV antibody by enzyme-linked immunosorbent assay, and reactive specimens were further tested by Western blot. None of the 102 specimens were seropositive for HTLV. Our findings provide no evidence for an HTLV-like virus in New World primates from Panama, but the sample size was small, and further studies are warranted.

Role of sucrose in colonization of Streptococcus mutans in conventional Sprague-Dawley rats.

The role of sucrose in the colonization of S mutans strain 6715 in conventional Sprague-Dawley rats was studied. A diet with 56% sucrose favored the oral colonization of the test strain compared to diets with 56% glucose or fructose or to laboratory chow as determined by recoveries from extracted teeth ground in tissue grinders. S mutans strain 6715 cells became well established in all rats fed a high sucrose diet with cell inoculums ranging from 10(8) to the lowest effective dose of 10(5) CFU once orally administered; in rats on nonsucrose diets, inoculation with even the highest dose only infrequently resulted in the establishment of S mutans strain 6715. Sucrose- and glucose- grown cells appeared to behave similarly. Colonization of S mutans strain 6715 occurred in all rats fed diets with a sucrose content ranging from 56 to as low as 1%. The establishment of S mutans strain 6715 on the teeth of rats fed diets with a sucrose concentration of 0.1 or 0.01% was impaired and comparable to the diet containing 56% glucose. In rats fed a high glucose diet, uniform establishment and persistence of the test strain occurred after frequent inoculations with about 5 X 10(8) CFU. The colonization under these conditions appeared to be independent of the intestinal canal as a bacterial cell source. These data suggest the possibility that S mutans can establish itself in the human mouth in the absence of dietary sucrose. In rats fed a high glucose diet and inoculated with 10(7) CFU or less, the cells gradually disappeared from the teeth; in contrast, the test strain implanted well in rats fed the sucrose favors firmer attachment of initially weakly attached cells via in situ new glucan synthesis. S mutans strain 6715 also appeared to have some affinity for teeth in the absence of dietary sucrose that may be of ecological significance. Once firmly established in rats fed a high sucrose diet, S mutans strain 6715 maintained itself in high numbers on the teeth after a switch to a high glucose diet during a 14-week period.

Utilization of ketorolac tromethamine for control of severe odontogenic pain.

Ketorolac tromethamine (KT) (Toradol, 60 mg to 2 ml), an injectable nonsteroidal anti-inflammatory drug, was compared with a placebo (sodium chloride, 0.9%) for analgesic effects in patients presenting with severe odontogenic pain. Utilizing a double-blind protocol, KT and placebo were administered and evaluated. Forty patients presenting with severe odontogenic pain (75 to 100 mm and above utilizing the visual analog scale of 100 mm) recorded their visual analog scale score once every 10 min for 90 min after injection of either KT or placebo and before initiating traditional incision and drainage, endodontic therapy, and/or extraction. Results indicate that KT patients had significantly less pain from 20 to 90 min postadministration than those receiving placebo. By the 90-min period, KT patients were reporting negligible discomfort. Observed side effects included lightheadedness and injection site pain. It was concluded that KT effectively reduces severe odontogenic pain within 40 min after administration in human subjects, with minimal side effects.

Unusual pattern of pulp canal obliteration following luxation injury.

Pulp canal obliteration can occur as a result of tooth injury. A case report is presented in which a 6-yr-old patient developed partial pulp canal obliteration of a maxillary central incisor 9 months after luxation injury. The mineralization created unusual canal morphology which presented some difficulty in endodontic treatment of the tooth.

Heat transfer to the periodontal ligament during root obturation procedures using an in vitro model.

It appears to be important to avoid thermal injury to the periodontal ligament when using heated guttapercha techniques such as "System B." An in vitro model was developed, consisting of an extracted human tooth rooted in an artificial periodontal ligament (PDL) and alveolar socket, which allowed us to measure the temperature transferred to the root surface. The teeth were instrumented and subsequently embedded in alginate to simulate the PDL. Medium gutta-percha points were fit, sealer was applied, and a fine Buchanan plugger was used for condensation. Temperature measurements were taken simultaneously at the apex and 5 mm from the apex during obturation with two fine gauge thermocouples connected to a digital thermometer. The average temperature increase was approximately 1 degree C at the apex and approximately 2 degrees C at the 5 mm mark. The resulting temperature increases appear to be lower than previously reported by other investigators (Hardie, 1986, 1987; Barkhordar et al., 1990; Weller et al., 1991; Lee et al., 1998), who did not allow for the heat disseminating effect of the PDL.

Microwave-assisted extraction of C60 and C70 from fullerene soot.

Microwave-assisted extraction (MAE) was examined as an alternative to the traditional Soxhlet method of extracting C(60) and C(70) from fullerene soot. MAE of 0.20 g of fullerene soot with 95:5 toluene-acetonitrile yielded greater than 7.8 mg of C(60) and greater than 0.54 mg of C(70) in 4 min with no further increase in yield after 30 min of irradiation. By comparison, exhaustive Soxhlet extraction of the same size sample with the same solvent yielded 7.1 mg of C(60) and 0.58 mg of C(70) in 340 min. Re-extraction by MAE of soot initially extracted by Soxhlet increased the yield of Soxhlet alone. Although MAE was limited to less than 0.5-g sample per extraction vessel, multiple samples were extracted with minimal increased extraction time and no reduction in the amount of material recovered.

In vivo comparison of Visualix-2 and Ektaspeed Plus in the assessment of periradicular lesion dimensions.

UNLABELLED: Accurate assessment of intraosseous lesion dimensions is useful in determining strategies for treatment of periradicular pathoses of dental causation. OBJECTIVES: To compare the efficacy of digital versus analog imaging for the measurement of mesiodistal and vertical dimensions of periapical lesions in patients that require apical surgery. METHODS: Fourteen examiners assessed the dimensions of 28 lesions with a millimeter ruler and Ektaspeed Plus radiographs (Eastman Kodak, Rochester, N.Y.), and with the Visualix-2 (Gendex/Dentsply, Milan, Italy) in unenhanced, contrast-stretched and equalized modes with proprietary software mouse-driven measurement algorithm. Impregum F (Premier Dental Products) impressions at surgery were used as the "gold standard." Ten randomly chosen images were reread 2 weeks later to assess intra-operator reliability. As the Mauchly sphericity test was significant for all tests, a multivariate analysis of variance was used to assess accuracy. To explain the exact difference between means, the Bonferroni test was applied. Intra-observer reliability was assessed with Friedman's two-way analysis of variance; inter-observer effects were determined with Cronbach's alpha. RESULTS: For accuracy in measurement, the closest to the "gold standard" were achieved with the Visualix-2 with image equalization. The contrast-stretched Visualix-2 and unenhanced Visualix-2 measurements were less accurate; conventional film was consistently the least accurate (p < 0.002). On the other hand, subjective preference placed film radiographs above the unenhanced Visualix-2 images; contrast-stretched Visualix-2 images were preferred over all other modalities. CONCLUSIONS: Charge-coupled device-based images with the Visualix-2 are preferable to film-based radiographs for measuring periapical lesion dimensions.

Orofacial and craniofacial pain. Primary care concerns.

A patient who experiences an acute episode of oral or facial pain is likely to consult a primary care physician. Dr Green reviews the basic information needed to distinguish among the more common types and causes of such pain. Once the pain's source is determined, treatment can be prescribed or an appropriate referral made.

Relationship between the concentration of bacteria in saliva and the colonization of teeth in humans.

The relationship between the salivary concentration of bacteria and their number that can be recovered from tooth surfaces has been studied in 12 human subjects. The mean salivary concentration of naturally occurring Steptococcus mutans and lactobacilli, determined on selective media, was 3.7 x 10(5) and 3.8 x 10(5) colony-forming units (CFU) per ml, respectively. In subjects with salivary concentrations of S. mutans of about 10(4) CFU/ml or less or about 10(5) CFU/ml or less of lactobacilli, these organisms could not be isolated from cleaned teeth after 2 to 3 h of oral exposure. In experiments with streptomycin-labeled S. sanguis cells held in the mouth for 15 min, the minimal salivary concentration required for their recovery from the teeth was about 10(3) CFU/ml. Both S. mutans and lactobacilli were found to be highly localized on teeth. This evidence suggests that the concentrations of S. mutans and lactobacilli generally present in saliva are insufficient for the initiation of their firm attachment to relatively nonretentive tooth surfaces. The low efficiency of their intraoral spread, as suggested by their highly localized distribution on teeth, or of their transmission between subjects may be essentially due to the interrelated factors bacterial affinity and number of colony-forming units available for attachment.

Sugar Concentrations in Guard Cells of Vicia faba Illuminated with Red or Blue Light : Analysis by High Performance Liquid Chromatography.

Concentrations of soluble sugars in guard cells in detached, sonicated epidermis from Vicia faba leaves were analyzed quantitatively by high performance liquid chromatography to determine the extent to which sugars could contribute to changes in the osmotic potentials of guard cells during stomatal opening. Stomata were illuminated over a period of 4 hours with saturating levels of red or blue light, or a combination of red and blue light. When stomata were irradiated for 3 hours with red light (50 micromoles per square meter per second) in a solution of 5 millimolar KCl and 0.1 millimolar CaCl(2), stomatal apertures increased a net maximum of 6.7 micrometers and the concentration of total soluble sugar was 289 femtomoles per guard cell (70% sucrose, 30% fructose). In an identical solution, 2.5 hours of irradiation with 25 micromoles per square meter per second of blue light caused a maximum net increase of 7.1 micrometers in stomatal aperture and the total soluble sugar concentration was 550 femtomoles per guard cell (91% sucrose, 9% fructose). Illumination with blue light at 25 micromoles per square meter per second in a solution lacking KCl caused a maximum net increase in stomatal aperture of 3.5 micrometers and the sugar concentration was 382 femtomoles per guard cell (82% sucrose, 18% fructose). In dual beam experiments, stomata irradiated with 50 micromoles per square meter per second of red light opened steadily with a concomitant increase in sugar production. Addition of 25 micromoles per square meter per second of blue light caused a further net gain of 3.7 micrometers in stomatal aperture and, after 2 hours, sugar concentrations had increased by an additional 138 femtomoles per guard cell. Experiments with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) were performed with epidermis illuminated with 50 micromoles per square meter per second of red light or with 25 micromoles per square meter per second of blue light in solutions containing or lacking KCl. DCMU completely inhibited sugar production under red light, had no effect on guard cell sugar production under blue light when KCl was present, and inhibited sugar production by about 50% when guard cells were illuminated with blue light in solutions lacking KCl. We conclude that soluble sugars can contribute significantly to the osmoregulation of guard cells in detached leaf epidermis of V. faba. These results are consistent with the operation of two different sugar-producing pathways in guard cells: a photosynthetic carbon reduction pathway and a pathway of blue light-induced starch degradation.

Effect of sodium hexanitrocobaltate (III) decomposition on its staining of intracellular potassium ions.

The effect was examined of the chemical decomposition of the potassium stain sodium hexanitrocobaltate (III) (SHC), on its ability to produce stain granules of consistent size that could be used to estimate the K+ contents of stomatal guard cells. Stomata in detached epidermis from leaves of Vicia faba (fava bean) were stimulated to accumulate K+ by treating them with fusicoccin. Stomatal apertures and the fraction of guard cell area covered by K+ precipitate granules (K+ score) were measured by digitizing photographic enlargements, and K+ scores were correlated with the age of stain that had been stored either in open or closed containers. The ability of stain aged in open containers to produce consistent fractional cell coverage was compared to 1) the ability of identically treated stain to precipitate K+ from solutions of KCI, and to 2) the kinetics of decomposition of SHC. It was found that the fractional coverage of guard cells of stomata opened to the same apertures decreased with a first order rate constant of 2.3 x 10(-5)/sec. The mass of precipitate formed by treatment of KCl solutions was unchanged for 2 hr after initial preparation of the SHC, and decreased thereafter with a first order rate constant of 1.0 x 10(-5)/sec. When stored in tightly sealed containers, nearly 100 hr were required for an occasionally opened bottle of SHC to decay to the same efficacy as a solution left open to the air for 8 hr.

A High-Affinity Hemoglobin Is Expressed in the Notochord of Amphioxus, Branchiostoma californiense.

In the phylum Chordata, only members of the subphylum Vertebrata were thought to express hemoglobin (Hb). Here we document the existence of intracellular Hb expressed in members of the subphylum Cephalochordata. Hemoglobin is expressed in myotome tissue and in notochord cells within the body of amphioxus. Both notochord and myotome tissue Hbs have a molecular size consistent with a dimeric molecule made up of two non-covalently linked monomers each of approximately 19 kD. The notochord Hb has a relatively high oxygen-binding affinity, with an apparent P5O of 0.036 kPa (0.27mm Hg), and it does not bind oxygen cooperatively. The notochord Hb may be involved in facilitating oxygen delivery and providing a short-term oxygen store within the notochord cells in order to maintain a high level of aerobic metabolism in support of the sustained contraction necessary for notochord function.