Antibodies against Periodontal Microorganisms and Cognition in Older Adults.

INTRODUCTION: Markers of poor oral health are associated with impaired cognition and higher risk of Alzheimer disease (AD) and thus may help predict AD. OBJECTIVES: The aim of this study was to evaluate the cross-sectional association between empirically derived groups of 19 IgG antibodies against periodontal microorganisms and cognition in middle-aged and older adults. METHODS: The study population consisted of participants of the third National Health and Nutrition Examination Survey (NHANES III) (1988 to 1994), who were 60 y and older, among whom cognition and IgG antibodies against 19 periodontal microorganisms were measured (N = 5,162). RESULTS: In multivariable quantile regression analyses, the Orange-Red (Prevotella melaninogenica, Prevotella intermedia, Prevotella nigrescens, Porphyromonas gingivalis) and Yellow-Orange (Staphylococcus intermedius, Streptococcus oralis, Streptococcus mutans, Fusobacterium nucleatum, Peptostreptococcus micros, Capnocytophaga ochracea) cluster scores were negatively associated with cognition. A 1-unit higher cluster score for the Orange-Red cluster was associated on average with a lower cognitive score (ß for 30th quantile = -0.2640; 95% confidence interval [CI], -0.3431 to -0.1848). Similarly, a 1-unit higher score for the Yellow-Orange cluster was associated with a lower cognitive score (ß for 30th quantile = -0.2445; 95% CI, -0.3517 to -0.1372). CONCLUSION: Groups of IgG antibodies against periodontal microorganisms were associated with lower cognition among free living adults 60 years and older, who were previously undiagnosed with cognitive impairment. Though poor oral health precedes the development of dementia and AD, oral health information is currently not used, to our knowledge, to predict dementia or AD risk. Combining our findings with current algorithms may improve risk prediction for dementia and AD. KNOWLEDGE TRANSLATION STATEMENT: IgG antibodies against periodontal microorganisms were associated with lower cognition among adults 60 years and older previously undiagnosed with cognitive impairment. Periodontal disease may predict cognition among older adults.

An ultrastructural and functional characterization of rat somatotrophs highly enriched on a continuous Percoll density gradient.

We here describe the use of a continuous Percoll density gradient in preparing a fraction of consistently more than 95% rat somatotrophs. Recovery was about 50% and cell viability 98-99.5%. Two groups of somatotrophs were identified, one (74-82%, type II) heavily and another (18-26%, type I) sparsely granulated. Freshly prepared somatotrophs responded to growth hormone-releasing factor but the responsiveness was greatly enhanced after 3 days' culture. Electron microscopy revealed a well-preserved morphological integrity in both freshly prepared and cultured somatotrophs. culture reduced the average granule profile area and granule volume density of type II cells. This population of pure and well-functioning somatotrophs is suited for studies on the cellular mechanisms involved in growth hormone secretion.

Morphometry of Rambourg-positive and Rambourg-negative beta-cell granules after culture with low and high glucose concentrations.

Dispersed islet cells from noninbred ob/ob mice were cultured for 3 days with 3 or 20 mM D-glucose and silver stained according to Rambourg et al. Two tinctorial subsets of dark and light intracellular granules were analyzed by morphometry at the ultrastructural level. The two types of granules were similar in size and shape. However, with 3 mM glucose the dark granule cores were surrounded by larger vesicles than the light granules. With 20 mM glucose, both types of granule vesicles and cores became smaller and dark-granule cores became more rounded, compared with cultures with 3 mM glucose. The higher glucose concentration also induced a marked decrease in the number (-84%) and volume density (-90%) of dark granules. In contrast, the number of light granules increased (+60%) with maintenance of their volume density. We suggest that the dark Rambourg-positive and the light Rambourg-negative beta-cell granules are functionally distinct subsets. The dark granules are probably engaged in insulin discharge. We discuss the unclear role of the light granules with a view to previously postulated heterogeneities of the insulin granule pool and their significance for exocytosis and intracellular hormone degradation.

Quantitative energy dispersive X-ray microanalysis of eight elements in pancreatic endocrine and exocrine cells after cryo-fixation.

Quantitative X-ray microanalysis of 8 elements was performed on ultrathin, freeze-dried sections of islets and pancreas pieces from non-inbred ob/ob-mice. Diffusion of elements was reduced to a minimum by rapidly freezing the tissue samples between nitrogen-cooled polished copper surfaces and avoiding the use of chemical fixatives and stains. The ultrastructural morphology was adequately maintained to allow measurements on secretory granules, mitochondria, cell nuclei, and cytoplasm free of these organelles. The distribution of the various elements between cellular compartments was similar in islet beta-cells and exocrine pancreas cells. However, the insulin secretory granules were outstanding in exhibiting the highest concentrations of zinc and calcium. In comparison with cytoplasm in the beta-cells, the insulin granules accumulated calcium 2-fold and zinc as much as 40-fold. As no correlation could be made for endoplasmic reticulum in the cytoplasmic measurements areas, the true accumulations above cytosol are likely to be even higher.

Morphogenetic effects of glucose on mouse islet-cell re-aggregation in culture.

The re-aggregation of dispersed islet cells from non-inbred ob/ob-mice was studied by light and electron microscopy. After 3 days of culture, spontaneously formed aggregates with more than 95% beta-cells were up to 0.5 mm in diameter and exhibited a high degree of viability on dye exclusion tests. In comparison with cultures at 1 or 3 mM D-glucose, or 1 mM D-glucose in combination with 19 mM 3-0-methyl-D-glucose, aggregates formed in 20 mM D-glucose were more closely packed, had a smoother circumference with elongated peripheral beta-cells, and exhibited well developed micro-villi in localized intercellular widenings. A stereological analysis of electron micrographs showed that beta-cells aggregated at 20 mM D-glucose exhibited the same individual profile area but a significantly lower form factor, and a significant reduction in granule volume density as compared with aggregates at 3 mM D-glucose. It is concluded that D-glucose has morphogenetic effects on both the cellular and the micro-anatomical level of pseudo-islet structure in culture.

Diethyldithiocarbamate, but not disulfiram, inhibits alloxan-induced dye accumulation of isolated mouse islet beta-cells.

The diabetogenic action of alloxan on pancreatic beta-cells is thought to be mediated by hydroxyl radicals. The initial attack of the radicals is probably at the plasma membrane level. Diethyldithiocarbamate (DDTC) and its dimer disulfiram (Antabuse) have recently been shown to protect against damage by free radical generating agents. The ability of DDTC and disulfiram to inhibit alloxan-induced dye accumulation of isolated ob/ob mice islet beta-cells was therefore studied. Evans blue was used as an indicator of plasma membrane permeability. DDTC (100 microM 1 mM) but not disulfiram (100 microM 1 mM) inhibited alloxan-induced dye uptake of beta-cells. The effect of DDTC on oxygen consumption in a mixture of reduced glutathione (GSH), alloxan and FeSO4 was studied with a Clark-type oxygen electrode. DDTC (20, 100 microM) had no effect on the oxygen consumption of this mixture. It is suggested that the DDTC inhibition of alloxan-induced dye uptake of isolated beta-cells takes place at a step beyond the generation of free radicals.

Influence of fixation and staining techniques on the ultrastructure of the insulin secretory granule.

The ultrastructure of beta-cell granules was examined after fixation of isolated mouse islets in fixatives of various compositions. Islets fixed in glutaraldehyde with or without post-fixing in osmium tetroxide, or in osmium tetroxide alone, exhibited the classical picture of electron-dense core surrounded by a lucid halo. After fixation in potassium permanganate, with or without post-fixing in osmium, the secretory vesicle was often completely filled with a fairly homogeneous material; the vesicle membrane was distinct in outline. When glutaraldehyde-fixed beta-cells were stained according to Rambourg to visualize reducing groups, possibly carbohydrates, two distinct classes of secretory granules were observed, one darkly stained and one faintly, without any noticeable precipitation of silver; the perigranular halo remained unstained in both types of granules. The perigranular halo of aldehyde and osmium fixed beta-granules also remained unstained in cells exposed to the osmiophilic amine, 5,6-dihydroxytryptamine.

Ultrastructure and membrane permeability of cultured pancreatic beta-cells exposed to alloxan or 6-hydroxydopamine.

Stereological techniques on electron microscopy micrographs were used to evaluate the morphological changes of cultured islet beta cells that had been exposed to alloxan or 6-hydroxydopamine. Trypan Blue exclusion by cells cultured for 3 days indicated that the cells were 100% viable. Electron microscopy revealed that nearly all of the surviving cultured cells were beta cells. Exposure to 5 mmol/l alloxan or 1-5 mmol/l 6-hydroxydopamine for 10 or 30 min caused a general swelling of the cultured cells with a concomitant swelling of mitochondria and nuclei. The size of the secretory granules was not affected by the drugs. Only 3-10% of the cells excluded Trypan Blue after exposure to 5 mmol/l alloxan or 6-hydroxydopamine. The data conform with the hypothesis that a primary action of alloxan and 6-hydroxydopamine is at the plasma membrane level of beta cells.