The relationship between biologic concepts and fabrication of surgical guides for dental implant placement

This article reviews guidelines for construction of surgical guides to direct dental implant placement. Biologic principles are discussed with regard to the mesiodistal, buccolingual, and apicocoronal insertion of implants. The application of these data to develop surgical guides is discussed. Also, with respect to specific prosthetic reconstructions, a variety of guides are described that can be fabricated for partially and fully edentulous arches.     

Studies on the effect of vanadate on endocytosis and shape changes in human red blood cells and ghosts

When amphipathic cationic drugs are added to intact human RBCs, the RBCs first undergo a stomatocytic shape change and then, if relatively large amounts of drug are added and if the metabolic state of the RBC is appropriate, endocytic vacuoles form. Vanadate has a structural similarity to the transition state of phosphate, which presumably accounts for its ability to inhibit phosphohydrolases, although other actions of vanadate have been described. Vanadate inhibited three forms of drug-induced endocytosis in intact RBCs despite the fact that the three drugs chosen (primaquine, chlorpromazine, and vinblastine) are known to have differing requirements for RBC ATP. Vanadate also inhibited the stomatocytic shape change produced by primaquine, chlorpromazine, and vinblastine, but not the stomatocytosis produced by low pH. Vanadate had no effect on RBC echinocytosis produced by lysophosphatidylcholine. In studying endocytosis in hypotonic, leaky, "white" ghosts, we discovered that vanadate inhibited only the endocytosis produced by Mg-ATP and not the endocytosis produced by manipulations that directly attack the cytoskeletal proteins. These findings suggest that ATP hydrolysis has a role in some forms of amphipathic cation-induced stomatocytosis and endocytosis in intact RBCs. In addition, studies in ghosts support the idea that Mg-ATP does indeed produce "energized" endocytosis dependent on utilization or hydrolysis of ATP.     

Molecular characterization of a high A2 beta thalassemia by direct sequencing of single strand enriched amplified genomic DNA

Two families, one of Anglo-Saxon-Dutch descent, and the other, West Indian black, have an atypical beta thalassemia characterized by an unusually high level of Hb A2 in the heterozygous state. Restriction endonuclease mapping showed a deletion of about 1.35 kilobase (kb) in the 5' region of the beta globin gene. Direct sequencing of a specific region of genomic DNA amplified by a new modification of the polymerase chain reaction defined the deletion to be 1,393 base pairs (bp) and to be the same in both families. The deletion extends from 485 bp 5' to the mRNA CAP site to the middle of the second intervening sequence. This deletion, together with three others previously described that remove the 5' end of the beta gene but leave the delta gene intact, are all associated with unusually high levels of Hb A2 in the heterozygous state.     

Childhood cardiac function after twin-to-twin transfusion syndrome – a 10-year follow up

Aim:  To perform a 10-year follow up of cardiac structure and function after twin-to-twin transfusion syndrome (TTTS) – a severe foetal circulatory complication associated with myocardial hypertrophy in the recipient twin.
Methods:  Cardiac dimensions, systolic and diastolic function as assessed by echocardiography including flow and tissue Doppler velocimetry in 22 healthy survivors of TTTS with a mean age of 9.6 (7.2–11.8) years.
Results:  The donor and recipient twin did not show any differences in end-diastolic ventricular size, interventricular septum thickness, diameter of right ventricular outflow tract, cardiac valves, coronary arteries or in systolic blood flow velocities. However, compared with the donors, the recipients had significantly lower E/A ratios because of lower E-waves in both mitral (−0.15 ± 0.10, p < 0.01) and tricuspid (−0.09 ± 0.07, p < 0.01) valves, indicating reduced early diastolic ventricular fillings compared with donors.
Conclusion:  At school age, twins surviving TTTS had a cardiac structure and function within normal range. There were no differences in heart structure or systolic ventricular function between twins but, compared with the donor twin, we found a reduced early diastolic function in the recipient.     

Predictors and Sequelae of Smoking Topography Over the Course of a Single Cigarette in Adolescent Light Smokers

PurposeThe objective of this study was to determine whether adolescent smokers, who varied in their smoking histories and symptoms of nicotine dependence, exhibit any decrease in puff volume and duration similar to that typically seen in dependent adolescent and adult smokers. Moreover, we examined whether puffing trajectories were moderated by individual difference factors, as well as whether puffing topography over the course of smoking a single cigarette was predictive of an escalation in dependence symptoms.MethodsWe assessed smoking topography (puff number, duration, volume, maximum flow rate [velocity], and inter-puff interval) over the course of smoking a single cigarette in a sample of 78 adolescent light smokers, using hierarchical linear modeling. We examined moderators (anxiety, depression, nicotine dependence) of the topographic trajectories, as well as whether smoking topography predicted any change in dependence over a 2-year period.ResultsPuff volume and puff duration decreased over the course of smoking the cigarette, whereas puff velocity and inter-puff interval increased. Slopes for puff volume and duration were moderated by anxiety and depressive symptoms. Moreover, individuals with a less “typical” topography pattern (exhibited stable or increasing volume and duration over the course of smoking the cigarette) demonstrated a heightened dependence escalation in the subsequent 2 years.ConclusionOur findings suggest that adolescent light smokers self-regulate nicotine during the course of smoking a single cigarette, similar to that reported in dependent adolescent and adult smokers. However, single cigarette self-regulation was influenced by certain affective factors. Implications of these findings and future directions for adolescent smoking research are discussed.