Prophylactic platelet administration during massive transfusion. A prospective, randomized, double-blind clinical study.

Prior studies at Harborview Medical Center have suggested that dilutional thrombocytopenia is a major etiology of microvascular, nonmechanical bleeding (MVB). We undertook a prospective randomized double-blind clinical study to compare the prophylactic effects of 6 units of platelet concentrates (PLT) versus 2 units of fresh frozen plasma (FFP) administered with every 12 units of modified whole blood in patients undergoing massive transfusion (12 or more units in 12 hours). After exclusions, three of 17 patients who received PLT and three of 16 patients who received FFP developed MVB, an incidence no different from our previous findings. Regression lines of platelet counts during transfusion were no different between groups, and both groups had higher platelet counts than predicted from a standard washout equation. Only one patient had evidence of dilutional thrombocytopenia as a cause for MVB. Prophylactic platelet administration is not warranted as a routine measure to prevent MVB.     

Temporal pattern of stimulation of osteoblast-associated genes during mechanically-induced osteogenesis in vivo: early responses of osteocalcin and type I collagen.

Mechanical loading is an essential environmental factor in skeletal homeostasis, but the response of osteoblast-associated genes to mechanical osteogenic signal is largely unknown. This study uses our recently characterized in vivo osteoinductive model to analyze the sequence of stimulation and the time course of expression of osteoblast-associated genes in mechanically loaded mouse periodontium. Temporal pattern of regulation of osteocalcin (OC), alkaline phosphatase (ALP), and type I collagen (collagen I) was determined during mechanically-induced osteoblast differentiation in vivo, using a mouse tooth movement model earlier shown to induce bone formation and cell-specific regulation of genes in osteoblasts. The expression of target genes was determined after 1, 2, 3, 4, and 6 days of orthodontic movement of the mouse first molar. mRNA levels were measured in the layer of osteoblasts adjacent to the alveolar bone surface, using in situ hybridization and a relative quantitative video image analysis of cell-specific hybridization intensity, with non-osseous mesenchymal periodontal cells as an internal standard. After 24 hours of loading, the level of OC in osteoblasts slightly decreased, followed by a remarkable 4.6-fold cell-specific stimulation between 1 and 2 days of treatment. The high level expression of OC was maintained throughout the treatment with a peak 7-fold stimulation at day 4. The expression of collagen I gene was not significantly affected after 1 day, but it was stimulated 3-fold at day 2, and maintained at a similar level through day 6. The ALP gene, which we previously found to be mechanically stimulated during the first 24 hours, remained enhanced from 1.8- to 2.2-fold throughout the 6 days of treatment. Thus, in an intact alveolar bone compartment, mechanical loading resulted in a defined temporal sequence of induction of osteoblast-associated genes. Stimulation of OC 48 h after the onset of loading (and 24 h prior to deposition of osteoid) temporally coincided with that of collagen I, and was preceded for 24 h by an enhancement of ALP. Identification of OC as a mechanically responsive gene induced in functionally active osteoblasts in this study is consistent with its potential role in limiting the rate of mechanically-induced bone modeling. Furthermore, these results show that temporal progression of mechanically-induced osteoblast phenotype in this in vivo model occurs very rapidly. This suggests that physiologically relevant mechanical osteoinductive signal in vivo is targeting a population of committed osteoblast precursor cells that are capable of rapidly responding by entering a differentiation pathway and initiating an anabolic skeletal adaptation process.     

Ultrasound determination of the relationship of radioactive plaques to the base of choroidal melanomas

There is an assumption that radioactive plaques placed at surgery are, and will remain, in proper relationship to the base of the tumor. The plaque dose is calculated based on this assumption. In fact, factors such as loose sutures, improper diameter estimations, pressure from adjacent rectus muscles, and intervening tissue (oblique muscles) can compromise this relationship. Ultrasound provides a practical method of imaging the tumor and plaque simultaneously. The authors have used postoperative ultrasound to monitor the accuracy of iodine-125 plaque placement in nine cases. Detection of eccentrically placed and malpositioned plaques provides valuable insight which can be used to refine surgical technique. Detection of plaque tilting by oblique muscles can serve as a basis for recalculating dosage. The relationship of plaque margins to vital ocular structures such as the optic nerve can also be determined by ultrasound.     

Monoamine oxidase activity in rat and human odontoblasts: a microgasometric study

The microgasometric method was used for determination of MAO activity in single odontoblasts isolated from rat and man. By using tyramine as a substrate, the presence of MAO in these cells was demonstrated. Both molecular forms of MAO, MAO A and MAO B, were found using specific inhibitors clorgyline and deprenyl.     

Dental archforms in dentoalveolar Class I,II and III

Objective:To test the hypothesis that no differences exist in dental arch dimensions between dentoalveolar Classes I, II, and III, and between male and female subjects, as measured on virtual three-dimensional (3D) models.Materials and Methods:Samples included randomly selected plaster dental casts of 137 white patients (43 Class I, 50 Class II, and 44 Class III) from the Department of Orthodontics, School of Dental Medicine, University of Zagreb, Croatia. Dental models were scanned and digitized using ATOS II SO (“Small Objects”) scanning technology (GOM mbH, Braunschweig, Germany). Eight linear and two proportional measurements were calculated for both upper and lower dental arches.Results:In men, a significant difference in the upper dental arch was present in the incisor region, and in the lower dental arch, differences were found in intercanine and intermolar widths (P < .05). Significant differences were noted between male groups in the upper molar depth dimension (P  =  .022) and in the lower molar and canine depth dimensions (P < .05). Class III males had the greatest lower molar and canine width/depth ratios and the smallest lower canine depth/molar depth ratio. Class III women had wider and shorter mandibular arches when compared with Class I and Class II females.Conclusion:The hypothesis was rejected. The dimensions of the dental arches are related to gender and to dentoalveolar class. Class I and II subjects have similar dimensions of maxillary dental arch, but Class II subjects have a transverse deficit in the mandible. In Class III subjects, the maxillary dental arch is insufficient in transverse and sagittal dimensions, and the mandibular arch dominates in the transverse but not in the sagittal dimension.     

The effect of chronic hypercalcemia or hypocalcemia on the follicular and parafollicular cells in rat thyroid gland

In three experiments of 30 weeks' duration, 93 adult female Wistar rats received controlled amounts of calcium with food and water, to produce a state of either hypercalcemia or hypocalcemia. A systematic sterological analysis of the thyroid glands and a radioimmunological analysis of thyroxine, triiodothyronine, and thyrotropine were performed. In the hypercalcemic rats, a reactive hyperplasia of the parafollicular cells was established; this was accompanied by morphological and biochemical signs of hyperfunction of the follicular cells, despite a reduced central stimulation by thyrotropin. In the hypocalcemic animals, no quantitative morphological changes in the parafollicular cells were observed; however, morphological and biochemical signs of hypofunction of the follicular cells were obvious, despite stronger central stimulation by thyrotropin. It is concluded that the extrinsic regulation of follicular cells by the blood calcium level is stronger than the intrinsic regulation by hypothalamo-hypophyseal hormones.     

Ultrasound biomicroscopy in plateau iris syndrome.

Ultrasound biomicroscopy is a new technique that uses high-frequency ultrasound (50 to 100 MHz) to produce images of the entire anterior segment at high resolution (20 to 50 microns). The iridocorneal angle, iris, ciliary body, and posterior chamber can be imaged in detail and the dimensions and anatomic relationships of these structures determined. Plateau iris syndrome is a condition in which the angle remains appositionally closed or occludable after iridectomy for angle-closure glaucoma. How the iris remains in a position that allows it to occlude the angle has been uncertain. We performed ultrasound biomicroscopy eye examinations on eight patients with clinically diagnosed plateau iris syndrome. In all the patients, ciliary processes were situated anteriorly compared to the position in normal subjects and in patients with angle closure caused by pupillary block. The ciliary processes provide structural support beneath the peripheral iris, preventing the iris root from falling away from the trabecular meshwork after iridectomy.