Search PubMed⌕ Search

Biomedical subjects

R Lang

Publications and source records attributed to R Lang.

At least 37 records · Page 2Linked to original sources
PubMed2001

Screening, confirmation and quantification of diuretics in urine for doping control analysis by high-performance liquid chromatography-atmospheric pressure ionisation tandem mass spectrometry.

A sensitive, selective, robust and fast method to identify 32 diuretics and masking agents in urine is described. The analytical procedure is reduced to a single XAD extraction step for sample preparation, followed by reversed-phase liquid chromatography in combination with atmospheric pressure ionisation/tandem mass spectrometry. This technique is, after minor modifications, suitable for screening analyses and confirmation of identity as well as quantitation of diuretics. Considerations relating to the stability and metabolism of the compounds are given if relevant for routine screening analyses.

Atmospheric Pressure↗
PubMed2001

Cutting edge: Stat6-dependent substrate depletion regulates nitric oxide production.

The cytokines IL-4 and IL-13 inhibit the production of NO from activated macrophages through an unresolved molecular mechanism. We show here that IL-4 and IL-13 regulate NO production through depletion of arginine, the substrate of inducible NO synthase (iNOS). Inhibition of NO production from murine macrophages stimulated with LPS and IFN-gamma by IL-4 or IL-13 was dependent on Stat6, cell density in the cultures, and pretreatment for at least 6 h. IL-4/IL-13 did not interfere with the expression or activity of iNOS but up-regulated arginase I (the liver isoform of arginase) in a Stat6-dependent manner. Addition of exogenous arginine completely restored NO production in IL-4-treated macrophages. Furthermore, impaired killing of the intracellular pathogen Toxoplasma gondii in IL-4-treated macrophages was overcome by supplementing L-arginine. The simple system of regulated substrate competition between arginase and iNOS has implications for understanding the physiological regulation of NO production.

Animals↗
PubMed2001

Transcatheter closure of atrial septal defects and patent foramen ovale under intracardiac echocardiographic guidance: feasibility and comparison with transesophageal echocardiography.

Transesophageal echocardiography (TEE) has been employed successfully for guiding transcatheter device closure of secundum atrial septal defect (ASD) and patent foramen ovale (PFO). However, the use of TEE for device closure requires general anesthesia. Intracardiac echocardiography (ICE) can provide similar anatomical views that might replace the use of TEE for device closure. Eleven patients (eight female/three male) with secundum ASD and PFO associated with strokes underwent attempts at transcatheter closure of their defects under sequential TEE and ICE guidance (six patients) and under ICE alone (five patients). The ages of the patients ranged from 6.6 to 74.7 yr, and their weights ranged from 23 to 124.5 kg. The sizes of the defects, as measured by TEE (six patients), ranged from 3 to 27 mm and, as measured by ICE (11 patients), from 3 to 27 mm. The balloon-stretched diameter of the ASD, as measured by TEE (six patients), ranged from 16 to 38 mm and, as measured by ICE (11 patients), from 16 to 35 mm. Both techniques correlated well for the measured two-dimensional diameter and for the balloon-stretched diameter (r = 0.97 and 0.98, respectively). Both TEE and ICE provided similar views of the defects and the various stages of device deployment. Owing to the proximity of the left atrium to the esophagus, however, the images obtained by ICE were more helpful and informative than those obtained by TEE. All patients experienced successful device placement (six patients under both TEE and ICE; five patients under ICE guidance alone); complete closure of the defects was effected in nine patients, whereas two patients had small residual shunts. There were no complications. We conclude that ICE provides unique images of the atrial communications and measurements similar to those obtained by TEE. ICE potentially could replace TEE as a guiding imaging tool for ASD and PFO device closure, thus eliminating the need for general anesthesia.

Adolescent↗
PubMed2001

Multiple roles of neurotrypsin in tissue morphogenesis and nervous system development suggested by the mRNA expression pattern.

We have mapped the spatio-temporal expression of the multidomain serine protease neurotrypsin in the developing mouse by in situ hybridization. On embryonic day (E) 8, mRNA is detected in giant trophoblast cells, later in embryonic mesenchymal tissues. On E11, expression begins in Schwann cell precursors, olfactory epithelium, trigeminal ganglion, and midbrain. The floor plate shows strong expression on E12. Further prenatal development is characterized by rising neurotrypsin mRNA in sensory ganglia and motor neurons. Staining in cerebral cortex emerges around birth and culminates toward the end of the first week with a complex laminar and areal pattern. Expression in peripheral nerves and nonneural tissues vanishes soon after birth and the adult neuronal distribution is gradually established until weaning age. This developmental expression pattern suggests roles of neurotrypsin in morphogenesis of nonneural tissues, as well as in neural development, in particular in axonal target invasion, synaptogenesis, and Schwann cell differentiation.

Aging↗
PubMed2001

Glass fiber-reinforced abutments for dental implants. A pilot study.

Titanium abutments in dental implants shine through all-ceramic crowns and therefore limit excellent esthetic results. Prototypes of tooth-colored fiber-reinforced abutments were investigated to avoid the shining-through effect. In vitro, the fracture strength was determined after thermal cycling and mechanical loading of all-ceramic single crowns and four-unit bridges made of a fiber-reinforced composite. The suprastructures were adhesively fixed onto fiber-reinforced implant abutments and compared with those fixed on standard titanium abutments. The median of the fracture strength of the titanium-supported all-ceramic crowns was significantly higher than the median of crowns fixed onto the prototypes. But this value was still more than twice as high as the maximum loading force under oral conditions. No statistical difference was found between four-unit bridges made by fiber-reinforced composite inserted onto titanium abutments and those inserted onto fiber-reinforced abutments. Fiber-reinforced abutment prototypes for dental implants avoided the shining-through effect associated with metal abutments. Their load-bearing capacity after in vitro stress simulation was higher than the maximum oral loading force. With some improvements, the fiber-reinforced implant abutments are therefore a promising alternative to titanium abutments.

Composite Resins↗
PubMed2001

Glass-fibre-reinforced-composite fixed partial dentures on dental implants.

UNLABELLED: The objective was to investigate the fracture strength and marginal fit of implant suprastructures made of fibre-reinforced composite which were fixed onto the implants using cementation or screws. A sample (n=8) of 4-unit bridges, made of the fibre-reinforced composite Vectris/Targis, were adhesively cemented onto titanium conical implant abutments. The second sample consisted of eight screwable Vectris/Targis bridges which were based on prototypes of titanium crown bases. After a 5 year simulation of thermal cycling and mechanical loading (TCML), all specimen were loaded to fracture. Marginal fit was investigated using a semiquantitative SEM analysis. The cemented 4-unit bridges showed a fracture strength of 1553 N (Q1=1498 N, Q3=1825 N) and the screw-fixed bridges had a median of 1457 N (Q1=1223 N, Q3= 1781 N). The analysis of the marginal adaptation showed similar results of cemented and screwed bridges. The bond between the Targis facing-material and the composite cement was significantly deteriorated after TCML. CONCLUSION: Suprastructures made of glass-fibre-reinforced composite could become an alternative to reconstructions with a metal-framework. Both, fixation onto the implants with screws or cementation, are possible.

Composite Resins↗
PubMed2001

Enhanced detection criteria in implantable cardioverter defibrillators: sensitivity and specificity of the stability algorithm at different heart rates.

The lack of specificity in the detection of ventricular tachyarrhythmias remains a major clinical problem in the therapy with ICDs. The stability criterion has been shown to be useful in discriminating ventricular tachyarrhythmias characterized by a small variation in cycle lengths from AF with rapid ventricular response presenting a higher degree of variability of RR intervals. But RR variability decreases with increasing heart rate during AF. Therefore, the aim of the study was to determine if the sensitivity and specificity of the STABILITY algorithm for spontaneous tachyarrhythmias is related to ventricular rate. Forty-two patients who had received an ICD (CPI Ventak Mini I, II, III or Ventak AV) were enrolled in the study. Two hundred ninety-eight episodes of AF with rapid ventricular response and 817 episodes of ventricular tachyarrhythmias were analyzed. Sensitivity and specificity in the detection of ventricular tachyarrhythmias were calculated at different heart rates. When a stability value of 30 ms was programmed the result was a sensitivity of 82.7% and a specificity of 91.4% in the detection of slow ventricular tachyarrhythmias (heart rate < 150 beats/min). When faster ventricular tachyarrhythmias with rates between 150 and 169 beats/min (170-189 beats/min) were analyzed, a stability value of 30 ms provided a sensitivity of 94.5% (94.7%) and a specificity of 76.5% (54.0%). For arrhythmia episodes > or = 190 beats/min, the same stability value resulted in a sensitivity of 78.2% and a specificity of 41.0%. Even when other stability values were taken into consideration, no acceptable sensitivity/specificity values could be obtained in this subgroup. RR variability decreases with increasing heart rate during AF while RR variability remains almost constant at different cycle lengths during ventricular tachyarrhythmias. Thus, acceptable performance of the STABILITY algorithm appears to be limited to ventricular rate zones < 170 beats/min.

Aged↗
PubMed2001

Excretion of sweat and urine pyridinoline crosslinks in healthy controls and subjects with established metabolic bone disease.

Convenient techniques for measuring rates of bone turnover have been developed in recent years with the advent of biochemical markers of bone metabolism. One recent of these techniques is a collection method and quantitative enzyme immunoassay for free pyridinoline crosslinks in human sweat. The concentrations of pyridinoline crosslinks in 5-day sweat collections and first morning void and 24-hour urine collections from healthy subjects and subjects with established metabolic bone disorders were determined. T-scores were higher in the sweat system than in the urine system by up to 10-fold in postmenopausal subjects, women with hyperparathyroidism, and subjects with postmenopausal osteoporosis. For subjects with postmenopausal osteoporosis, receiver-operating characteristic curve analysis yielded areas under the curve of 0.699, 0.629, and 0.520 for sweat pyridinoline, first morning void urine pyridinoline, and 24 hour urine pyridinoline respectively. The areas under the curve of the sweat and first morning void urine measurements were significantly greater (p<0.05) than the 24-hour pyridinoline measurements. Healthy postmenopausal subjects and subjects with postmenopausal osteoporosis were monitored before and during estrogen replacement therapy or alendronate therapy. Sweat pyridinoline values declined by 49.0 +/- 12.4% and 19.4 +/- 19.9% for estrogen and alendronate subjects respectively. We conclude that this non-invasive technique is a sensitive and specific measure of bone resorption and is appropriate as an adjunct to techniques such as bone density and may also be useful in monitoring of response to anti-resorptive therapies.

Adult↗
PubMed2001

Severe complications of varicella in previously healthy children in Germany: a 1-year survey.

OBJECTIVE: Varicella is a common infectious disease, usually benign and self-limited, and complications are believed to be rare. The purpose of this study was to describe the epidemiology of severe varicella complications in immunologically healthy children in Germany. METHODS: Information on any admission of children with a severe complication associated with chickenpox was solicited throughout 1997 from all 485 pediatric hospitals in Germany using an established surveillance system. The case definition included nonimmunocompromised individuals who were up to 16 years of age and hospitalized with neurologic complications, bacterial superinfections, or hematologic complications. RESULTS: The response rate to the surveillance questionnaire during the observation period was high: 93.4%. Of the 153 reported cases, 119 met the case definition. There was a seasonal distribution of reported complications with a peak in March. The majority of complications occurred in preschool-age children with a maximum age of 4 years. No gender predominance was found with a distribution of 56 female and 63 male patients. Multiple entries for complications were allowed. The most frequent complications were neurologic, which were reported in 73 children (61.3%); cerebellitis was the leading diagnosis (n = 48), followed by encephalitis (n = 22), meningitis (n = 2), and central facial palsy (n = 1). A total of 46 (38.6%) infectious complications were identified. Superinfections of the skin were present in 31 (26.0%), pyogenic arthritis was present in 5 (4.2%), osteomyelitis was present in 4 (3.3%), necrotizing fasciitis was present in 3 (2.5%), orbital cellulitis was present in 2 (1.6%), and pneumonia was present in 1 (0.8%). Streptococcus pyogenes was the leading cause of bacterial infections (18 cases [15.1%]), with invasive disease in 6 patients (8.4%) and linked to 4 of 8 cases with defect healing. Infectious complications were reported in the majority in younger children up to 4 years of age, whereas neurologic complications occurred more frequently in an older age range. Five children experienced thrombocytopenia or severe anemia. There was no bleeding disorder, no fatality, and no case of Reye syndrome reported during the 1-year observation period. In total, 8 (6.7%) of 119 patients reported having long-term sequelae, 6 attributable to infectious complications and 2 to persistent deficits after neurologic complications. CONCLUSION: This is the first prospective nationwide study of severe complications of varicella in immunologically healthy children. Related to 14 025 867 children up to the age of 16, a crude incidence of severe chickenpox complications of 0.85/100 000 could be calculated [corrected]. The actual hospitalization rate attributable to complicated chickenpox is probably much higher, because this calculation refers to a population theoretically at risk and not the truly susceptible individuals. The results of this study demonstrate considerable morbidity with a comparatively high rate of encephalitis, osteomyelitis, and pyogenic arthritis. Although infectious complications were present in only 38.6% of the reported cases, they contributed disproportionately to the cases with chronic sequelae. Looking at these cases in more detail, S pyogenes involvement was identified as the major risk factor for invasive disease with an unfavorable long-term outcome. varicella-zoster virus, chickenpox/epidemiology, chickenpox/complications, encephalitis, cellulitis, osteomyelitis, necrotizing fasciitis, group A beta-hemolytic streptococci, Europe.

Adolescent↗
PubMed2001

[Cytomeglovirus infection after liver transplantation].

OBJECTIVE: To study the prophylaxis, diagnosis and treatment of cytomegalovirus (CMV) infection after liver transplantation. METHODS: The clinical data of 10 patients receiving liver transplantation from July 1999 to October 2000 in our hospital were retrospectively analyzed along with literature review. RESULTS: CMV infection occurred asymptomatic cally in 6 patients, of whom, 5 were cured. CONCLUSIONS: Fluorogenic quantitative PCR (FQ-PCR) is effective, sensitive and highly specific for detecting CMV infection. It is important to monitor the status of CMV infection in patients receiving liver transplantation preoperatively and postoperatively. The key point for prophylaxis and treatment of CMV infection is early prevention and treatment after operation. Ganciclovir can exert significant therapeutic effects on CMV infection.

Adult↗
PubMed2000

Interferon-beta treatment in multiple sclerosis patients decreases the number of circulating T cells producing interferon-gamma and interleukin-4.

Systemic administration of interferon (IFN)-beta has been recently approved for the treatment of relapsing-remitting multiple sclerosis (RRMS). The immunological mechanism by which IFN-beta ameliorates MS is still partially unknown. We measured the number of blood circulating CD4(+), CD4(-), CD8(+), and CD8(-) T cells secreting IFN-gamma and IL-4 in 26 RRMS patients followed for up to 9 months of an alternate day s.c. treatment with 8x16 IU of IFN-beta1b. Compared to pre-treatment values, a significant (P<0.05) reduction of CD4(+), CD4(-), CD8(+) and CD8(-) cells producing IFN-gamma and of CD4(+) and CD4(-) cells producing IL-4 was observed in MS patients. The IFN-beta-associated effect was evident soon after the beginning of the treatment and persisted for the entire follow-up period. We did not observe any effect of IFN-beta treatment on the percentage of IL-4-producing CD8(+) and CD8(-) cells nor in that of natural killer (NK) cells producing IFN-gamma. Our results show that IFN-beta treatment in MS patients induces a profound and persistent down-regulation of the number of circulating T cells secreting IFN-gamma and IL-4 thus suggesting a broader rather than a specific immunomodulatory effect of IFN-beta in MS.

Adjuvants, Immunologic↗
PubMed2000

Dephasing times in quantum dots due to elastic LO phonon-carrier collisions

Interpretation of experiments on quantum dot (QD) lasers presents a challenge: the phonon bottleneck, which should strongly suppress relaxation and dephasing of the discrete energy states, often seems to be inoperative. We suggest and develop a theory for an intrinsic mechanism for dephasing in QDs: second-order elastic interaction between quantum dot charge carriers and LO phonons. The calculated dephasing times are of the order of 200 fs at room temperature, consistent with experiments. The phonon bottleneck thus does not prevent significant room temperature dephasing.

Journal Article↗
PubMed2000

Effects of inotropic stimulation on segmental left ventricular relaxation quantified by color kinesis.

Although myocardial ischemia impairs left ventricular (LV) relaxation before contractile function, regional LV diastolic dysfunction is difficult to evaluate by conventional echocardiography. Because beta-adrenergic stimulation enhances myocardial relaxation, we sought to characterize segmental LV diastolic function (by color kinesis) during dobutamine stress echocardiography and compare it with independently assessed segmental systolic function. We studied 22 patients with suspected coronary artery disease with color kinesis by acquiring digital images with endocardial motion display throughout diastole. Quantification of LV segmental diastolic peak filling rate (SPFR, normalized to segmental end-diastolic area/s) was obtained at rest, low-dose, and peak dobutamine infusion in myocardial segments visualized from the short-axis and/or apical 4-chamber views. In patients with resting normal LV systolic function and a dobutamine-induced hypercontractile response (group I, n = 13 patients; 102 segments), progressive increases in SPFR (p <0.001) were seen in all segments. However, in LV segments with resting systolic wall motion abnormalities (group II, n = 9 patients; 74 segments) SPFR measured at rest was significantly lower than that in group I (p <0.005) and did not increase significantly in response to dobutamine. In both groups of patients, LV myocardial segments (n = 528; rest and after dobutamine)-systolic and quantitative diastolic function-were concordant in 84% and 77% as viewed from short-axis and apical views, respectively. Thus, segmental LV diastolic function can be measured with color kinesis at rest and after inotropic stimulation, allowing comparison with segmental systolic function during pharmacologic stress testing.

Aged↗
PubMed2000

Comparison of failure rates of adhesive-fixed partial dentures for in vivo and in vitro studies.

The objective was to investigate associations between the results of an in vitro and an in vivo study using an artificial mouth and a study of adhesive fixed partial dentures (AFPD) begun in 1985 [1]. Twenty extracted human molars and 20 human upper incisors were inserted into PMMA resin, 6 mm apart to represent a gap. Two preparation methods (identical to those in in vivo conditions) were used: a retentive preparation technique (posterior) and a non-retentive preparation technique (anterior). The frameworks of the bridges consisted of CoCr-alloy with a ceramic veneered pontic to replace the missing tooth. The bonding surfaces of the posterior AFPDs were conditioned with a tribochemical system, while the anterior AFPDs were sandblasted. All AFPDs were inserted using a dual curing composite cement. During thermal-cycling and mechanical loading (TCML: 6000 x 5 degrees C, 1.2 x 10(6) x 50 N, 1.66 Hz) in an artificial environment, the frequency and type of failures were observed. The above mentioned loading parameters were hypothesized to represent a period of 5 years under oral conditions. The results were compared to those of similar bridge-types in the in vivo study. The Kaplan-Meier estimations showed similar graphs for in vivo and in vitro with both types of AFPDs. In vivo and in vitro, the retentively prepared AFPDs were markedly more successful. With regard to the failure types, the simulation-parameters seemed to represent a loading stress that was comparable to in vivo conditions.

Acid Etching, Dental↗
PubMed2000

Technical failure rates of double crown-retained removable partial dentures.

Removable partial dentures (RPD) can be retained using conical crowns or parallel-sided telescopic double crowns. The purpose of this study was to evaluate and compare the technical failure rate of the two retainer systems. One hundred seventeen dentures made by dentists of the medical school were included. Seventy-four RPD were retained with parallel-sided crowns (n = 251) and 43 with conical crowns (n = 160). Following the medical report follow-ups from January 1992 to December 1998, technical RPD failures were noted and analyzed. Technical problems occurred during the observation time in 48.8% of the conical retained dentures and 34.2% of the parallel-sided retained dentures. In both cases, loss of cementation was most frequently noted, while loss of the facings occurred only with conical crowns. Other technical failures did not depend on the type of retainer system used. These were most frequently problems with the denture base, e.g., fracture of artificial teeth or the metal framework. We conclude that there were different technical failures of both double crown retainer systems. These problems were not insignificant in number but treatable.

Cementation↗
PubMed2000

Experimental design of FPD made of all-ceramics and fibre-reinforced composite.

OBJECTIVES: This study was carried out to combine flexural properties of FRC materials with aesthetic values of ceramics. METHODS: The bonding strength of fibre-reinforced composite to ceramic was determined. Afterwards, 8 three unit and 8 four unit FPDs (fixed partial dentures) were manufactured based on the experimental design and were then adhesively luted onto human molars. After thermal cycling and mechanical loading in an artificial environment, the fracture strength and marginal adaptation was determined. FPDs made of FRC (fibre-reinforced composite) materials were used as a control. RESULTS: The most reliable bonding strength of ceramic to FRC material was achieved using acid etching in combination with adhesive luting techniques. Median fracture strength values of 575 N for three unit FPD and 876 N for four unit FPD were established. More than 85% of the experimental FPDs showed a perfect margin while less than 15% revealed a marginal gap, even after thermal cycling and mechanical loading (TCML). The strongest influence of TCML on the marginal adaptation of the experimental design FPD was determined within the four unit system showing approximately a 10% change in marginal gap and perfect margin. SIGNIFICANCE: Assuming an improvement in adhesive bonding between the ceramic and the FRC material and, in addition, an enhancement of the contact surface between pontic and abutment, the hybrid technique could represent an interesting procedure for further investigations and, eventually, clinical implication.

Acid Etching, Dental↗
PubMed2000

Flexural properties of fiber reinforced composite using a vacuum/pressure or a manual adaptation manufacturing process.

PURPOSE: This study investigated the influence of fiber content and water storage on the flexural strength of beams made of two fiber-reinforced composites (FRC), the Vectris and the FibreKor system. MATERIAL AND METHODS: A manual adaptation method (FibreKor, n=30) and a vacuum/pressure process (Vectris, n=30) were compared using 25x4x2mm(3) beams. One group of the Vectris (n=10) and the FibreKor beams (n=10) was stored in water for 24h, a further group was thermal-cycled (TC) 6000x5 degrees C/55 degrees C, and a third group was stored in water for 30days at 37 degrees C. All beams were then loaded to failure using a three-point bending test and the flexural strength was calculated. Finally, the fiber volume percent (vol%) was determined. RESULTS: Generally, the flexural strength decreased significantly with increasing storage time independent of the investigated fiber- and/or manufacturing system. With the parameters 24h/TC/30days, the mean of flexural strength for the Vectris beams was 618/579/545N/mm(2), and for FibreKor 585/534/499N/mm(2). A fiber content of 28.1+/-0.4vol% was assessed for the Vectris beams and 12.8+/-0.6vol% for the FibreKor beams. After 24h storage in water, the Vectris and the FibreKor beams demonstrated a statistically significant higher flexural strength than after 30days storage in water. CONCLUSIONS: A vacuum/pressure manufacturing process in contrast to manual adaptation, resulted in a markedly higher fiber content, but did not necessarily lead to significantly higher flexural strength. Not only the fiber content, but also matrix composition as well as the bond between fibers and matrix determined the properties of FRC.

Analysis of Variance↗