Estimation of instantaneous flow from the indicator-dilution curve after bolus injection of indicator

The indicator-dilution technique is commonly used to determine mean flow estimates. The estimation of instantaneous flow from the shape of an indicator-dilution curve is the objective of this study. Based on a mixing chamber approach to the flow system, a mathematical relationship is derived to reconstruct momentary flow from an indicator-dilution curve. This relationship is verified in a model setup both with only constant flow and with a sinusoidal flow variation superimposed. This method proved to give good flow estimates for limited values of flow parameters. Also, some preliminary experiments were performed in a pulsating flow system simulating heart action. The results were promising although the method proved to be very sensitive to baseline offset.     

Silicone implant for surgery of therapy-refractory glaucomas

A silicone implant for surgery of refractory glaucomas has been developed. It consists of a tube 0.64 mm in diameter glued to the upper surface of a plate resembling a contact lens. The surgical procedure, which is similar to a trabeculectomy, is described.     

Evidence for P2-purinoceptors on human osteoblast-like cells.

ATP released from damaged cells or by controlled secretion could be an important factor in the formation or remodeling of bone. In a variety of other tissues ATP has been shown to control cellular processes by acting on P2-purinoceptors and activating the calcium signaling pathway. Here we demonstrate for the first time that extracellular ATP increases the intracellular free calcium [Ca2+]i concentration in normal human osteoblasts and in SaOS-2 cells, a human osteosarcoma-derived cell line, but not in ROS 17/2.8 cells. The ATP-induced increase in [Ca2+]i was dose dependent, and the concentrations of ATP required were similar to those reported to regulate cellular functions in other cell types. Although ATP is metabolized rapidly by bone cells, the effects on [Ca2+]i appeared to be mediated directly by ATP rather than one of its metabolites. Adenosine 3-thiotriphosphate, a nonhydrolyzable analog of ATP, induced similar changes in [Ca2+]i. This indicates that P2-purinoceptors are present on osteoblast-like cells and that extracellular ATP from various sources might be an important factor in the regulation of osteoblast functions.     

Neuropathy with lysosomal changes in Marinesco-Sj?gren syndrome: fine structural findings in skeletal muscle and conjunctiva.

The light- and electron-microscopical findings in the skeletal muscle and conjunctiva of 6 patients with Marinesco-Sj?gren syndrome (MSS) were presented. All patients were related and showed the cardinal clinical symptoms of the syndrome: congenital cataracts, mental retardation, delayed statomotor development, and cerebellar ataxia. The most prominent alteration found in the skeletal muscle of four patients was extensive neurogenic atrophy with conspicuous groups of atrophic muscle fibers. Additional findings were vacuolar degeneration and secondary, unspecific changes like slight mitochondrial alterations and increased variability in muscle fiber calibers. The ultrastructural examination revealed double-membrane structures near to, but not in direct contact with the nucleus. The nuclear changes described earlier (7, 20) were not found in any of the cases. Conjunctival biopsies revealed a marked increase in the number of lysosomes in fibroblasts. In summary, to the well known myopathic damage of muscles in MSS a neurogenic component should be added. Disturbed lysosomal function is to be considered as the basic abnormality, though the enzyme defect has not yet been identified. In cases of clinically suspected MSS, examination of a conjunctival biopsy is highly recommended.     

Management of Patients After Catheter Ablation of Ventricular Tachycardia

The management of patients after catheter ablation of ventricular tachycardia is not well defined. In this article we summarize recently published results and report our own experience. Factors influencing the clinical outcome of these patients and methods to identify patients with an increased risk of recurrence of ventricular tachycardia are discussed. Furthermore, a review is given on current concomitant therapeutic tools including antiarrhythmic drugs and the implantation of an automatic cardioverter defibrillator.     

In vivo measurement of the shear modulus of the human vocal fold: interim results from eight patients

The shear modulus of the vocal fold is an essential parameter required to enhance our understanding of how the vocal fold operates, to develop mathematical models of phonatation, and to provide benchmarks to quantify the effectiveness of surgical procedures. The authors announced the successful deployment of an instrument to measure vocal fold elasticity in vivo last year, and now present the data taken from eight patients in vivo. The shear modulus was measured at the mid-membranous point, in a transverse direction with respect to the axis drawn between the anterior commissure and vocal process. The range of mean shear modulus results is 701–2,225 Pa, with a mean value of 1,371 Pa.     

Effect of titanium surface texture on the cell-biomaterial interface.

To improve the in vivo performance of engineered implants, this study examines the independent effects of surface chemistry and topography on fibroblast morphology and density in vitro. Titanium (Ti) was sputter-coated onto smooth and microtextured polyethylene terephthalate (PET). Test specimens were evaluated in 24-h, fibroblast cultures and assessed with scanning electron microscopy (SEM) for cellular morphology and density. Fibroblast density increased, as the Ti film thickness increased. The fibroblasts exhibited contact guidance on the textured test specimens. The greatest cellular density was found on the Ti-coated, textured test specimens. In conclusion, Ti and surface texture appeared to strongly influence fibroblast density and morphology as compared to PET and smooth surfaces.     

The effect of estrogens and dietary calcium deficiency on the extracellular matrix of articular cartilage in G?ttingen miniature pigs.

Clinical observations have suggested that estrogens are involved in the pathogenesis of postmenopausal osteoarthritis (OA). However, positive and negative associations between the incidence of OA and serum estrogen concentrations have been reported. In contrast to this, osteoporosis is regarded as a disease with a strong estrogen-dependent component. Moreover, there is an interaction between estrogen and calcium deficiency: calcium supplementation potentiates the effect of estrogen therapy. The present study was designed to investigate how estrogen deficiency affects the articular cartilage depending on calcium supply. The distribution of different types of glycosaminoglycans and collagens can be used as an indicator for extracellular matrix changes induced by estrogen deficiency. Different levels of dietary calcium were therefore fed to intact and ovariectomized G?ttingen miniature pigs for one year before articular cartilage was harvested. The histochemical staining for heavy sulfated glycosaminoglycans in the extracellular matrix of ovariectomized miniature pigs, especially of those fed with a low calcium diet, was stronger in comparison to intact animals. In intact animals type II-collagen was immunodetected in all zones of unmineralized and mineralized articular cartilage, while immunostaining for this protein was negative to weak in the deep radiated fiber zone of ovariectomized minipigs. These results suggest that the synthesis of heavy sulfated glycosaminoglycans and immunohistochemically detectable type II-collagen is possibly influenced by estrogen deficiency. In conclusion, under estrogen deficiency, the extracellular matrix of articular cartilage underwent similar changes to those observed in physiologically aging cartilage where keratan sulfate is increased as a heavy sulfated glycosaminoglycan.