Wallace W. Ambrose

The effect of a re-wetting agent on dentin bonding

OBJECTIVES Recently, a new generation of simplified one-bottle dentin bonding systems, sensitive to variations in the degree of substrate moisture, was introduced. This in vitro project compared the dentin bond strengths and interfacial ultra-morphology formed by three one-bottle bonding systems [OptiBond SOLO (ethanol-based), Prime&Bond 2.1 (acetone-based), and Single Bond (ethanol- and water-based)]. The null hypothesis tested was that re-wetting a dried dentin surface with a HEMA aqueous solution would not result in bond strengths, and resin impregnation into demineralized dentin, comparable to those obtained for moist dentin. METHODS Dentin specimens were assigned to the following three etched surface conditions: moist dentin-control group; dentin dried for 5 s; and dentin dried for 5 s and re-moistened with a commercial 35% HEMA aqueous solution. Mean shear bond strengths were calculated and analyzed with one- and two-way ANOVA. Dentin discs treated with the same combination of surface condition/adhesive were processed and observed under both transmission and scanning electron microscopes. RESULTS For moist dentin, the morphology of the resin-dentin interfaces showed penetration of the dentin adhesives to the depth of the transition between demineralized and unaffected dentin. Drying dentin for 5 s resulted in a significant decrease in mean bond strengths and an incompletely infiltrated collagen structure with areas of unveiled collagen fibers, regardless of the solvent. Re-wetting dentin with the aqueous HEMA solution re-established the level of bond strengths obtained to moist dentin and resulted in a raise of the fiber network with simultaneous increase in interfibrillar space dimensions. SIGNIFICANCE The results suggest that the use of an aqueous HEMA solution might compensate for the dryness induced on dentin surfaces by using air blasts from an air syringe, after rinsing off the etchant. As the behavior of the material that contained water was also affected by surface dryness, the percentage of water included in the composition of current ethanol- and water-based adhesives, such as Single Bond, may not be enough to compensate for the collapse of the collagen filigree upon drying.

Synergistic Pathogenicity of Porphyromonas gingivalis and Fusobacterium nucleatum in the Mouse Subcutaneous Chamber Model

Porphyromonas gingivalis and Fusobacterium nucleatum are often coisolated from sites of infection, such as suppurative apical periodontitis. The synergistic pathogenicity of mixed infection of P. gingivalis HG 405 with F. nucleatum PK 1594 was studied in the mouse subcutaneous chamber model in groups of seven animals. The minimal dose for P. gingivalis HG 405 that was required to infect 100% of the chambers was reduced by 1,000-fold when animals were inoculated in the same chamber with 1 x 10(9)F. nucleatum PK 1594 (p < 0.001). To benefit from the presence of the fusobacteria, P. gingivalis HG 405 had to be coinoculated; inoculation in separate chambers for the same animal had no such effect (p < 0.001). Subinfective F. nucleatum inocula also benefited from the association with P. gingivalis HG 405 and uniformly established an infection when this partner was present (p < 0.001). These results suggest that the frequent and natural coexistence of P. gingivalis and F. nucleatum in diseased sites may express such a synergism in successful establishment and survival of small inocula.

Peripheral neuropathy in mouse hereditary diabetes mellitus. I. Comparison of neurologic, histologic, and morphometric parameters with dystonic mice.

SummaryC57BL/KsJdb/db inbred mice have an hereditary autosomal recessive disease resembling in some respects maturity onset human diabetes mellitus. At 8–11 months of age, they displayed intermittent symptoms suggestive of a mild sensory neuropathy. These symptoms consisted of adduction of their hind limbs and flexing hind paws when raised by the tail, and inability to maintain their position on the roto wheel. Peripheral nerves and sensory ganglia of the diabetic mice were compared with those of the unafflicted littermates and studied with respect to Schwann cell counts and myclinated nerve fiber diameter measurements. In addition, teased fibers of peripheral nerves were compared for obvious changes in internodal distance and demyelination. Chromatolytic neurons were more abundant in lumbosacral spinal ganglia of diabetic mice than in corresponding ganglia of controls or in more anterior spinal ganglia and trigeminal ganglia of diabetics. Histologic studies showed an increase in Schwann cell counts in longitudinal sections of peripheral nerves. A similar but larger increase was observed in peripheral nerves of mice affected with an hereditary sensory neuropathy, dystonia musculorum. A small but general decrease in myelinated fiber diameter was observed in sensory and motor nerves.

L-Carnitine prevents mitochondrial damage induced by octanoic acid in the rat choroid plexus.

Cytochrome oxidase activity was investigated histochemically in the choroid plexus epithelium. Intense staining for the enzyme was exclusively limited to the mitochondria. Rats treated with octanoic acid displayed extensive ultrastructural disruptions in the epithelial cells of the choroid plexus. Mitochondria were fewer in number and more disrupted compared to the control. The enzyme activity was greatly reduced. However, pretreatment with an equimolar dose of L-carnitine followed by octanoic acid injection produced little alteration of either ultrastructure or enzyme staining. This study suggests that L-carnitine supplementation may restore mitochondrial function of the choroid plexus subjected to toxic organic anions in metabolic disorders, and may be useful in the prevention of metabolic encephalopathy.

Cytochemical correlates of structural sexual dimorphism in glandular tissues of the mouse

SummaryCirculating androgens are known to effect a sexual dimorphism of the submandibular gland and kidney of the mouse. Enzyme histocytochemical differences that correlate with these structural changes have been the subject of much study, especially in the kidney. In the present study, emphasis was placed on the hypogonadic effects of diabetes mellitus on the submandibular gland and kidney of C57BL/KsJ db/db inbred mice with an autosomal recessive disease resembling maturity onset human diabetes mellitus. These glands of adult diabetic mice of both sexes were compared with those of unafflicted heterozygous littermates. The mitochondrial cytochrome oxidase and peroxisomal and cytoplasmic catalase were studied in their submandibular glands and kidneys. The parasympathetic innervation of the submandibular glands was studied by a histochemical method for acetylcholinesterase. The extensive differentiation of striated ducts of the submandibular gland into granular tubules in the postpubertal male mouse was readily evident with the cytochrome oxidase procedure. This differentiation resulted in ductal staining patterns characteristic of the sexes. Alteration of these patterns suggested that demasculinization or feminization was occuring in the male diabetic mice and that masculinization or virilization (defeminization) was occurring in the female diabetics. Similarly, in kidney, study of the parietal epithelium of Bowmans capsule revealed feminization in the male diabetics and masculinization in the female diabetics. With the catalase procedure, a dramatic sexual dimorphism was observed in the kidneys of the heterozygous unafflicted mice. Peroxisomal staining of epithelial cells of the proximal convoluted tubules was much more intense in the outer medulla of the male than of the female. In kidneys of the diabetics, the staining patterns again suggested that feminization of the male and masculinization of the female kidneys had occurred. On the other hand, neither a sexual dichotomy nor effects due to diabetes could be observed in the characteristic catalase staining observed in the luminal epithelial cells of submandibular gland distal ducts. The parasympathetic innervation of the submandibular gland, as revealed by the acetylcholinesterase method, was also markedly sexually dimorphic in the unafflicted mice. This was due to the more extensive innervation of the larger granular ducts characteristic of male than of the smaller striated ducts of the female. As a result of diabetes, the innervation and duct size decreased in the submandibular gland of the male, suggesting feminization, whereas they increased in the female suggesting masculinization. These changes were consistent with those observed in submandibular with the cytochrome oxidase procedure. Attempts were made to interrelate all of the enzyme histochemical changes observed in submandibular gland and kidney with the weights of these glands, sex, gonadal weights, diabetic status and urinary protein excretion. Generally, significant differences were recorded which suggested that the feminization of the submandibular gland and kidney in the diabetic male mice, and their masculinization in the female diabetics, were due to the hypogonadism of the disease.

Intracellular calcite and sulfur dynamics of Achromatium cells observed in a lab-based enrichment and aerobic incubation experiment

AbstractWe investigated the intracellular dynamics of calcite and sulfur in the large sulfur-oxidizing, calcite-accumulating bacterium Achromatium, with an emphasis on oxygen exposure as a physiological control. For this purpose, morphological changes and possible accretion mechanisms of calcite granules in cells that were freshly collected from natural Achromatium-containing sediment were compared to cells from the same source after prolonged exposure to atmospheric oxygen. Intracellular sulfur is oxidized and removed in response to oxygen exposure. Calcite granules also undergo distinct oxygen-related dynamics; they alternate between tightly packaged, smooth granules with narrow but sharply defined interstitial spaces in atmospheric oxygen-exposed cells, and more loosely packaged granules with irregular, bumpy surface texture and larger interstitial spaces in cells that were not artificially exposed to oxygen. These results suggest that morphological changes of the calcite granules reflect their changing physiological role inside the cell. Sulfur oxidation and calcite dissolution appear to be linked in that proton generation during sulfur oxidation is buffered by gradual calcite erosion, visible in the smooth, rounded surface morphology observed after oxygen exposure. Our results support the hypothesis that calcite dynamics buffer the intracellular pH fluctuations linked to electron acceptor limitation during proton-consuming sulfide oxidation to sulfur, and electron acceptor abundance during proton-generating sulfur oxidation to sulfate.

Significance of Improved Cytochemical Methods for Hemoprotein Enzymes in Diagnosis and Classification of Leukemia

Success in achieving remissions of acute myelogenous leukemia (AML) since the 1950s, and especially since the mid-1970s, has developed a need for greater attention on the part of physicians to improved methods for diagnosing and classifying the leukemias. The majority of AML patients can achieve first remissions, some (5–10%) lasting several years; these prolonged survivors are presumably cured of their leukemia. Many AML patients, however, are still not receiving the benefits of improved diagnostic methods and intensive therapeutic regimens. Of the latter group 80% are dead within a year of diagnosis [1].