Salivary nitrate--an ecological factor in reducing oral acidity

Human oral cavities represent a novel environment with a constant supply of concentrated nitrate. For humans, over 80% of dietary nitrate originates from fruit and vegetables. With a healthy, balanced diet, rich in fruit and vegetables, the concentration of nitrate in saliva can reach up to more than three times the European drinking water standard. The physiological function of the active excretion of salivary nitrate is unknown. Furthermore, little is known of the ecological function of oral nitrate and the effect on the oral environment during its subsequent oral microbial conversions. The objectives of the research were to investigate the effect on salivary pH coupled with oral microbial nitrate and/or nitrite reduction. Human saliva samples were incubated anaerobically in the presence of 111.0 mmol glucose (2%), with and without 1.5 mmol nitrate/nitrite, and pH and nitrate/nitrite consumption were measured during the time-course of the incubations. We found that anaerobic incubation of saliva containing a mixture of oral bacteria in the presence of nitrate/nitrite substrates and glucose resulted in a higher pH than was found in controls in the absence of nitrate/nitrite. These results suggest that the presence of these electron acceptors repressed acid fermentation, or increased alkali production, or consumed acid produced, thus reducing salivary acidity. This finding identifies salivary nitrate as a possible ecological factor in reducing oral acidity. The possibility that a symbiotic relationship between host nitrate excretion and nitrate-reducing microorganisms might help to protect against tooth decay should be explored further.     

Effects of storage, RNA extraction, genechip type, and donor sex on gene expression profiling of human whole blood

BACKGROUND: Gene expression profiling of whole blood may be useful for monitoring toxicological exposure and for diagnosis and monitoring of various diseases. Several methods are available that can be used to transport, store, and extract RNA from whole blood, but it is not clear which procedures alter results. In addition, characterization of interindividual and sex-based variation in gene expression is needed to understand sources and extent of variability. METHODS: Whole blood was obtained from adult male and female volunteers (n = 42) and stored at various temperatures for various lengths of time. RNA was isolated and RNA quality analyzed. Affymetrix GeneChips (n = 23) were used to characterize gene expression profiles (GEPs) and to determine the effects on GEP of storage conditions, extraction techniques, types of GeneChip, or donor sex. Hierarchical clustering and principal component analysis were used to assess interindividual differences. Regression analysis was used to assess the relative impact of the studied variables. RESULTS: Storage of blood samples for >1 week at 4 degrees C diminished subsequent RNA quality. Interindividual GEP differences were seen, but larger effects were observed related to RNA extraction technique, GeneChip, and donor sex. The relative importance of the variables was as follows: storage < genechip < extraction technique < donor sex. CONCLUSION: Sample storage and extraction methods and interindividual differences, particularly donor sex, affect GEP of human whole blood.     

Factitious diarrhea induced by stimulant laxatives: accuracy of diagnosis by a clinical reference laboratory using thin layer chromatography

BACKGROUND: Surreptitious ingestion of laxatives can lead to serious factitious diseases that are difficult to diagnose. Most cases involve ingestion of bisacodyl or senna. Thin layer chromatography (TLC) of urine or stool is the only commercially available test for these laxatives. Such testing is considered highly reliable, but its accuracy in clinical practice is unknown. Our aim was to evaluate the reliability of TLC laxative testing by a clinical reference laboratory in the United States. METHODS: Diarrhea was induced in healthy volunteers by ingestion of bisacodyl, senna, or a control laxative (n = 11 for each laxative group). Samples of urine and diarrheal stool were sent in blinded fashion to the clinical reference laboratory for bisacodyl and senna analysis. RESULTS: TLC testing for bisacodyl-induced diarrhea revealed a sensitivity of 73% and specificity of 91% when urine was tested and sensitivity and specificity of 91% and 96%, respectively, when stool was analyzed. When diarrhea was induced by senna, the TLC assay for senna failed to identify even a single urine or stool specimen as positive (zero% sensitivity). CONCLUSIONS: Considering the expected prevalence of surreptitious laxative abuse in patients with chronic idiopathic diarrhea (2.4%-25%, depending on the clinical setting), TLC of urine or stool for bisacodyl by this reference laboratory would often produce misleading results, and testing for senna would have no clinical value. The major problems are false-positive tests for bisacodyl and false-negative tests for senna.     

Novel targets in deep brain stimulation for movement disorders

The neurosurgical treatment of movement disorders, primarily via deep brain stimulation (DBS), is a rapidly expanding and evolving field. Although conventional targets including the subthalamic nucleus (STN) and internal segment of the globus pallidus (GPi) for Parkinson’s disease and ventral intermediate nucleus of the thalams (VIM) for tremor provide substantial benefit in terms of both motor symptoms and quality of life, other targets for DBS have been explored in an effort to maximize clinical benefit and also avoid undesired adverse effects associated with stimulation. These novel targets primarily include the rostral zona incerta (rZI), caudal zona incerta (cZI)/posterior subthalamic area (PSA), prelemniscal radiation (Raprl), pedunculopontine nucleus (PPN), substantia nigra pars reticulata (SNr), centromedian/parafascicular (CM/PF) nucleus of the thalamus, nucleus basalis of Meynert (NBM), dentato-rubro-thalamic tract (DRTT), dentate nucleus of the cerebellum, external segment of the globus pallidus (GPe), and ventral oralis (VO) complex of the thalamus. However, reports of outcomes utilizing these targets are scattered and disparate. In order to provide a comprehensive resource for researchers and clinicians alike, we have summarized the existing literature surrounding these novel targets, including rationale for their use, neurosurgical techniques where relevant, outcomes and adverse effects of stimulation, and future directions for research.

     

A new quantitative nitroblue tetrazolium reduction assay based on kinetic colorimetry

A new method for the quantitative assay of nitroblue tetrazolium (NBT) in which the reduction is measured by kinetic colorimetric analysis is reported. The assay is conducted along standard conditions as far as neutrophil isolation and stimulation, except that the test is performed on microtiter plates and the change of color corresponding to NBT reduction is monitored on a kinetic enzyme immunoassay (EIA) reader for 25 min at 490 nm. The results are expressed as mOD/min/in. The influence of several parameters on the results of the assay was studied, including cell concentration, the nature and concentration of the stimulus, and the freshness of the reagents. Cell concentrations of 5 x 10(6) and 1 x 10(7)/ml were found to be optimal, and IgG-coated immunobeads, at a concentration of 1 mg/ml, were found to be the ideal stimuli. NBT reduction for nine normal volunteers studied at 5 x 10(6) cells/ml ranged from 1.80 to 7.30 mOD/min (mean +/- SD = 3.66 +/- 1.69). NBT reduction values at 1 x 10(7) cells/ml in six normal individuals ranged from 2.59 to 7.41 (4.73 +/- 1.89). In contrast, NBT reduction in a child with clinical symptoms suggestive of chronic granulomatous disease was 0.31 mOD/min. This method is considerably simpler than any alternative method for the performance of quantitative NBT assays.     

Right-to-left shunt across a patent foramen ovale caused by cardiac tamponade: diagnosis by transesophageal echocardiography

Cardiac tamponade can manifest as profound hypoxemia from intracardiac shunting across a patent foramen ovale. As a consequence, pulmonary embolus can be erroneously diagnosed. As demonstrated in the case described herein, transesophageal echocardiography can be useful in determining the correct diagnosis, especially if transthoracic echocardiography is technically limited. In our patient, the findings on transesophageal echocardiography also helped determine the appropriate treatment. The relative inaccessibility of the pericardial effusion to needle drainage prompted open surgical drainage.