Increase in cardiac output with rate-responsive pacemaker.

Patients with myocardial insufficiency or patients during high cardiac work loads increase cardiac output (CO) only through an increase in heart rate (HR), which is not possible with a VVI pacemaker. This clinical study tests the hypothesis that the respiratory-dependent pacemaker (RDP) is able to increase CO by an increase in HR. A multiprogrammable RDP (BIOrate RDP 2, Alpha, Köln, West Germany) was implanted in 21 patients (16 men and 5 women) for ventricular pacing. The mean age of the patients was 68.1 +/- 9.5 years (+/- standard deviation). Since the RDP can be programmed either in the RDP or VVI mode, all patients served as their own control. During follow-up examinations 4 to 6 weeks after implantation, an exercise ECG and a determination of CO during rest and exercise using equilibrium-radionuclide ventriculography were performed. One pacemaker has had to be explanted because of "end of life." No other RDP is malfunctioning. There was a significant increase in HR in all patients during exercise with the RDP versus the VVI mode (105.5 +/- 5.9 versus 84.5 +/- 7.0 bpm; p less than 0.05). CO increased during exercise to 10.6 +/- 0.8 L/min (VVI mode) and 12.7 +/- 1.5 L/min (RDP mode) (p = not significant). RDPs are reliable systems for patients in whom dual-chambered pacemakers are contraindicated (e.g., patients with bradyarrhythmias). The RDPs are able to increase CO by 26 to 35% compared with the VVI mode because of an increase in HR.

[Dilated pneumosinus of the frontal sinus]. / Pneumosinus dilatans der Stirnhöhle.

Pneumosinus dilatans is a rare disorder of the frontal sinus most commonly found in 20- to 40-year-old males. The deformity is caused by an abnormal enlargement of the frontal sinus by hyperpneumatization. A valve mechanism raising the pressure inside the sinus is regarded to be responsible for this condition. The diagnostic and surgical approach is presented in a 25-year-old male. A preoperative computed tomography (CT) scan in three planes illustrates the anatomical conditions and possible etiologic mechanisms. The surgical procedure is supposed to correct the esthetic deformity and the cause of the disorder. A bicoronal incision allows the best exposition of the frontal sinus. The osteoplastic correction is stabilized by titanium micro-osteosynthesis plates, which do not have to be removed. Functional endoscopic sinus surgery should be performed concomitantly in order to remove the cause of pneumosinus dilatans.

Photonic crystal tapers for ultracompact mode conversion.

We have studied the coupling of a classic ridge waveguide with a two-dimensional photonic crystal (PC) waveguide, using finite-difference time-domain calculations. The ridge waveguide exhibits only a weak refractive-index confinement of light, as it is commonly used in buried-heterostructure or ridge-waveguide lasers. The light is coupled to a PC waveguide that consists of one missing row along the ?K direction in a triangular lattice of air cylinders in AlGaAs. We compare various designs for PC tapers with that of a classic taper and for butt coupling. The calculation yields high coupling efficiency that exceeds 80% for a 2.5-microm-long PC taper. In addition, the dependence of the efficiency on the PC air-fill factor and on alignment tolerances is analyzed.

Glomerular and tubular proteinuria as markers of nephropathy in rheumatoid arthritis.

OBJECTIVE: We examined the prevalence of nephropathy in unselected patients with rheumatoid arthritis (RA) by measurement of marker proteins for glomerular and tubular damage in urine. METHODS: A highly sensitive immunoluminometric assay was used to measure albumin, immunoglobulin G and alpha1-microglobulin in 24 h urines of 44 RA patients and a control group of 46 patients with generalized osteoarthritis (OA). RESULTS: Fifty-five per cent of RA patients were found to have proteinuria as a symptom of renal disease. Drug therapy or vasculitis were identified as possible reasons for proteinuria in only 25% of these patients; in most patients (75%), no reason for proteinuria was found. Tubular and mixed proteinuria were more frequent than glomerular proteinuria. Only 15% of the control group exhibited mild proteinuria, which was attributable to nephrotoxic factors. The renal function of RA patients and the control group did not differ significantly. CONCLUSIONS: Proteinuria is a frequent symptom of nephropathy in RA. Screening for renal disease in RA should not only include creatinine measurement and dipstick examination of urine, but also more sensitive methods to detect tubular and glomerular proteinuria as a marker of tubular and early stages of glomerular damage.

[Mesenchymal stem cells--a new pathway for tissue engineering in reconstructive surgery]. / Adulte mesenchymale Stammzellen--neue Möglichkeiten der Gewebezüchtung für die plastisch-rekonstruktive Chirurgie. andreas.naumann@hno.med.uni-muenchen.de

INTRODUCTION: Mesenchymal stem cells (MSC) have the capacity to differentiate into chondrocytes with the synthesis of cartilage. This report presents the use of human adult bone marrow derived mesenchymal stem cells for tissue engineering of autologous cartilage grafts. METHODS: Human bone marrow aspirates were obtained from the iliac crest and fractionated on a Percoll gradient. The isolated hMSC were plated at 20 x 10 (6) cells per 100 mm (2) culture dish. After 21 days in culture at 37 degrees C with 5 % CO 2, the adherent multiplied MSC were trypsinized, counted, and tested for viability by trypan blue assay. The hMSCs were loaded into a sterile 15 ml polypropylene tube (0.5 Mio cells/ml) and centrifuged on the bottom of the tube at 500 g for 5 minutes. The MSC were cultivated for 3 weeks in vitro in a specific chondrogenetic medium composed of Dulbecco's Modified Eagles Medium-High Glucose supplemented with 10 ng/ml transforming growth factor-beta 1, 1 % ITS-Premix medium, 80 micro M ascorbic acid, and 100 nM dexamethasone. RESULTS: Histological and immunohistochemical studies performed after 3 weeks in three dimensional culture demonstrated the expression of cartilage specific collagen type II and X as well as proteoglycans. CONCLUSION: Human adult mesenchymal stem cells derived from bone marrow aspirates have the ability to differentiate into chondrocytes under specific culture conditions by growth factors. The use of adult mesenchymal stem cells may be a promising tool for tissue engineering of autologous cartilage grafts in reconstructive surgery in the future.