ATP gradients inhibit the migratory capacity of specific human dendritic cell types: implications for P2Y11 receptor signaling

Dendritic cells (DCs) are specialized antigen-presenting cells residing in tissues, from which they take up antigen. Activated DCs migrate through chemokine gradients from sites of inflammation to lymph nodes to stimulate T cells. At sites of inflammation, nucleotides, such as adenosine triphosphate (ATP), are released by activated or dying cells and can function as signaling molecules through P2 receptors (P2Rs). We investigated P2R expression in different DC populations and the effect of nucleotides on chemokine-directed migration. Exposure of monocyte-derived DCs (MoDCs) and CD1a+ dermal DCs to gradients of ATP inhibited their migratory capacity in a dose-dependent manner. Studies using P2R agonists and antagonists implicated signaling through the P2Y11R. On maturation, MoDCs down-regulated P2Y11R expression and were less sensitive to ATP-mediated inhibition of migration. In contrast, ATP did not inhibit the migration of CD1c+ peripheral blood (PB) DCs or interleukin-3 receptor-positive (IL-3R+) plasmacytoid DCs. Although all 4 DC populations expressed mRNA for P2Y11R, calcium-flux studies showed that blood DC types were unresponsive to P2Y11R agonists. In conclusion, DCs use distinct subtypes of P2R. The formation of ATP gradients at sites of inflammation may transiently inhibit the migration of local DCs, thus prolonging the time of antigen encounter. P2R inhibition may represent a new strategy to improve the migration of antigen-loaded DCs from the vaccination site to lymph nodes.     

Coagulation studies in rheumatic heart disease.

The clotting characteristics of pulmonary and systemic blood were studied in 10 patients with chronic rheumatic mitral valve disease complicated by atrial fibrillation and in seven patients with aortic valve disease in sinus rhythm. A haemostatic basis for the association of rheumatic mitral valve disease with thrombotic emboli was sought. Both groups of patients showed differences in platelet function between pulmonary and systemic arterial blood. In patients with mitral valve disease aggregation of platelets was significantly greater in pulmonary than in systemic arterial blood at rest; the converse was true during exercise. In aortic valve disease platelet aggregation was greater in systemic than in pulmonary arterial blood at all times. Only the patients with mitral valve disease showed changes in blood coagulation during passage through the lungs and left heart; there was a small but statistically significant shortening in partial thromboplastin time in systemic as compared with pulmonary arterial blood both at rest and during exercise. Similarly, the effects of exercise on the various haemostatic factors measured were largely confined to the patients with mitral valve disease; in these patients exercise stimulated an increase in factor VIII in pulmonary arterial blood and an increase in platelet adhesiveness and aggregability in left heart blood. These changes provide a basis for the suggestion that in patients with rheumatic mitral valve disease, unlike those with aortic valve disease, there is an increased thrombotic tendency in blood in the left heart which is particularly pronounced during exercise.     

Establishment of Parameters for Congenital Thoracic Stenosis: A Study of 700 Postmortem Specimens

Background

Congenital thoracic stenosis (CTS) occurs when the bony anatomy of the canal is smaller than expected in the general population. The diagnosis currently is made based on the clinical impression from subjective radiographic studies, and the normal values for CTS have not been established.

Questions/purposes

We provided a statistical definition for CTS based on objective measurements of thoracic spine specimens and explored parameters that might predict CTS.

Methods

We selected 700 adult skeletal specimens from the Hamann-Todd Collection in the Cleveland Museum of Natural History (Cleveland, OH, USA). We used calipers to measure the sagittal canal diameter (SCD), interpedicle distance (IPD), and pedicle length (PL). At each level, canal area was calculated using a geometric formula, a standard distribution was created, and values two SDs below the mean were considered congenitally stenotic. Corresponding values of SCD and IPD of the stenotic specimens were studied. The values of SCD and IPD predicting CTS with highest sensitivity and specificity were tabulated.

Results

At each level, CTS was defined as: T1, 160?mm²; T2, 135?mm²; T3, 131?mm²; T4, 130?mm², T5, 129?mm², T6, 127?mm²; T7, 127?mm²; T8, 129?mm²; T9, 130?mm²; T10, 132?mm²; T11, 140?mm²; and T12, 173?mm². A SCD less than 15?mm and an IPD less than 18.5?mm were predictive of CTS at each level with sensitivities and specificities of 80% to 100%.

Conclusions

We statistically defined CTS at each level. A SCD less than 15?mm or IPD less than 18.5?mm predicted the presence of CTS at all levels.

Clinical Relevance

In a symptomatic patient, on routine radiologic examination, a physician should suspect stenosis of the thoracic canal if the SCD and IPD are less than 15 and 18.5?mm respectively. As a spinal deformity surgeon, the canal area is especially relevant when considering a possible canal intrusion by implants.     

Microstructure and Elution of Tetracycline from Block Copolymer Coatings

A critical metrology issue for pharmaceutical industries is the application of analytical techniques for the characterization of drug delivery systems to address interrelationships between processing, structure, and drug release. In this study, cast coatings were formed from solutions of poly(styrene-b-isobutylene-b-styrene) (SIBS) and tetracycline in tetrahydrofuran (THF). These coatings were characterized by several imaging modalities, including time- of-flight secondary ion mass spectrometry (TOF-SIMS) for chemical imaging and analysis, atomic force microscopy (AFM) for determination of surface structure and morphology, and laser scanning confocal microscopy (LSCM), which was used to characterize the three-dimensional structure beneath the surface. The results showed phase separation between the drug and copolymer regions. The size of the tetracycline phase in the polymer matrix ranged from hundreds of nanometers to tens of microns, depending on coating composition. The mass of drug released was not found to be proportional to drug loading, because the size and spatial distribution of the drug phase varied with drug loading and solvent evaporation rate, which in turn affected the amount of drug released.     

Acute Severe Isovolemic Anemia Impairs Cognitive Function and Memory in Humans

Background: Erythrocytes are transfused to prevent or treat inadequate oxygen delivery resulting from insufficient hemoglobin concentration. Previous studies failed to find evidence of inadequate systemic oxygen delivery at a hemoglobin concentration of 5 g/dl. However, in those studies, sensitive, specific measures of critical organ function were not used. This study tested the hypothesis that acute severe decreases of hemoglobin concentration alters human cognitive function.

Methods: Nine healthy volunteers, age 29 +/- 5 yr (mean +/- SD), were tested with verbal memory and standard, computerized neuropsychologic tests before and after acute isovolemic reduction of their hemoglobin to 7, 6, and 5 g/dl and again after transfusion of their autologous erythrocytes to return their hemoglobin concentration to 7 g/dl. To control for duration of the experiment, each volunteer also completed the same tests on a separate day, without alteration of hemoglobin, at times of the day approximately equivalent to those on the experimental day.

Results: No test showed any change in reaction time or error rate at hemoglobin concentration of 7 g/dl compared with the data at the baseline hemoglobin concentration of 14 g/dl. Reaction time, but not error rate, for horizontal addition and digit-symbol substitution test (DSST) increased at hemoglobin 6 g/dl (mean horizontal addition, 19%; 95% confidence interval [CI], 4-34%; mean DSST, 10%; 95% CI, 4-17%) and further at 5 g/dl (mean horizontal addition, 43%; 95% CI, 6-79%; mean DSST, 18%; 95% CI, 4-31%). Immediate and delayed memory was degraded at hemoglobin 5 g/dl but not at 6 g/dl. Return of hemoglobin to 7 g/dl returned all tests to baseline, except for the DSST, which significantly improved, and returned to baseline the following morning after transfusion of all autologous erythrocytes.