Genetic predisposition for adult lactose intolerance and relation to diet, bone density, and bone fractures.

Evidence that genetic disposition for adult lactose intolerance significantly affects calcium intake, bone density, and fractures in postmenopausal women is presented. PCR-based genotyping of lactase gene polymorphisms may complement diagnostic procedures to identify persons at risk for both lactose malabsorption and osteoporosis. INTRODUCTION: Lactase deficiency is a common autosomal recessive condition resulting in decreased intestinal lactose degradation. A -13910 T/C dimorphism (LCT) near the lactase phlorizin hydrolase gene, reported to be strongly associated with adult lactase nonpersistence, may have an impact on calcium supply, bone density, and osteoporotic fractures in the elderly. MATERIALS AND METHODS: We determined LCT genotypes TT, TC, and CC in 258 postmenopausal women using a polymerase chain reaction-based assay. Genotypes were related to milk intolerance, nutritional calcium intake, intestinal calcium absorption, bone mineral density (BMD), and nonvertebral fractures. RESULTS: Twenty-four percent of all women were found to have CC genotypes and genetic lactase deficiency. Age-adjusted BMD at the hip in CC genotypes and at the spine in CC and TC genotypes was reduced by -7% to -11% depending on the site measured (p = 0.04). LCT(T/C-13910) polymorphisms alone accounted for 2-4% of BMD in a multiple regression model. Bone fracture incidence was significantly associated with CC genotypes (p = 0.001). Milk calcium intake was significantly lower (-55%, p = 0.004) and aversion to milk consumption was significantly higher (+166%, p = 0.01) in women with the CC genotype, but there were no differences in overall dietary calcium intake or in intestinal calcium absorption test values. CONCLUSION: The LCT(T/C-13910) polymorphism is associated with subjective milk intolerance, reduced milk calcium intake, and reduced BMD at the hip and the lumbar spine and may predispose to bone fractures. Genetic testing for lactase deficiency may complement indirect methods in the detection of individuals at risk for both lactose malabsorption and osteoporosis.     

Measurement of maximal power output in isokinetic and non-isokinetic cycling. A comparison of two methods

The main goal of the study was to compare maximal power output and power output at different pedalling frequencies obtained during isokinetic all-out tests with maximal power output obtained during a single all-out sprint (against the same braking force for every subject). Sixty healthy male subjects participated in the study. The ergometer system used in this study has three operating modes: the isokinetic mode (maintaining pedal crank velocity constant at a present level), a revolution dependent mode and a revolution independent mode. In all three operating modes the effective forces are monitored by means of strain gauge. All subjects performed a single all-out sprint against a braking force of 20 Newton and an all-out isokinetic cycling test consisting of ten 10 s bouts of maximal cycling at speeds ranging from 50 rpm to 140 rpm. In both tests, irrespective of which test mode was used, the mean power for a complete crank revolution showed parabolic relationships to crank velocity. For the isokinetic test, the subjects showed a peak power (IsoWpeak) of 15.3+/-1.7 W/kg corresponding to an optimal velocity of 115+/-8.6 rpm. For the force-velocity test NonisoWpeak (the highest power obtained at any time during the test) was 14.4+/-1.9 W/kg and was achieved at a pedalling rate of 127+/-14 rpm. IsoWpeak was significantly higher than NonisoWpeak (p<0.001) but there were no significant differences between NonisoWpeak and IsoWmax (maximal mean power for each full crank revolution) for the revolutions from 90 rpm to 140 rpm. Though, NonisoWpeak and IsoWpeak are significantly different, there was a strong relationship between NonisoWpeak and IsoWpeak (r = 0.7158, p<0.001). There was also a strong relationship between NonisoWpeak and IsoWmax for the revolutions from 50 rpm to 120 rpm (p<0.001) and at 130 rpm (p<0.01).     

Nonsyndromic types of ichthyoses – an update

Ichthyoses are genetically determined Mendelian disorders of cornification (MEDOC) that are characterized by universal scaling. Today we distinguish between non‐syndromic and syndromic forms. Ichthyosis vulgaris is the most frequent type (prevalence 1:100) and is caused by autosomal semi‐dominant filaggrin mutations. It is associated with a higher risk for the development of atopic diseases, such as atopic eczema and allergic rhinitis. Recessive X‐linked ichthyosis (RXLI) occurs almost exclusively in boys; in Germany it has a prevalence of around 1:4,000. It is caused by steroid sulfatase deficiency and is often associated with further clinical problems, such as cryptorchidism (～20%) or social communication deficits, such as attention deficit hyperactivity syndrome (40%) or autism (25%). Autosomal recessive congenital ichthyosis (ARCI) is genetically very heterogeneous and 8 different genes have been identified so far. The most frequent cause of ARCI is a transglutaminase 1 deficiency (prevalence 1:200, 000). Mutations in keratin genes are the cause of the keratinopathic ichthyoses, such as epidermolytic ichthyosis. They manifest at birth and often feature episodes of blistering. Most of these types are inherited as autosomal dominant traits, but autosomal recessive forms have also been described on occasion.     

Physiological Demands of Simulated Off-Road Cycling Competition

The purpose of the study was to measure the demands of off-road cycling via portable spirometry, leg-power output (PO), heart rate (HR) and blood lactate (BLa) concentration. Twenty-four male competitive cyclists (age: 29±7.2 yrs, height: 1.79 ± 0.05 m, body mass: 70.0 ± 4.9 kg, VO_2peak: 64.9 ± 7.5 ml·kg^-1·min^-1) performed simulated mountain bike competitions (COMP) and laboratory tests (LabT). From LabT, we determined maximal workload and first and second ventilatory thresholds (VT1, VT2). A high-performance athlete (HPA) was used for comparison with three groups of subjects with different sport-specific performance levels. Load profiles of COMP were also investigated during uphill, flat and downhill cycling. During the COMP, athletes achieved a mean oxygen uptake (VO_2COMP) of 57.0 ± 6.8 ml·kg^-1·min^-1 vs. 71.1 ml·kg^-1·min^-1 for the HPA. The PO_COMP was 2.66±0.43 W·kg^-1 and 3.52 W·kg^-1 for the HPA. PO_COMP, VO_2COMP and HR_COMP were compared to corresponding variables at the VT2 of LabT. LabT variables correlated with racing time (RT_COMP) and PO_COMP (p < 0.01 to <0.001; r-0.59 to -0.80). The VO_2peak (LabT) accounted for 65% of variance of a single COMP test. VO_2COMP, PO_COMP and also endurance variables measured from LabTs were found as important determinants for cross-country performance. The high average VO_2COMP indicates that a high aerobic capacity is a prerequisite for successful COMP. Findings derived from respiratory gas measures during COMPs might be useful when designing mountain bike specific training.

Key points

• Cross- country cycling is characterized by high oxygen costs due to the high muscle mass simultaneously working to fulfill the demands of this kind of sports.
• Heart rate and blood lactate concentration measures are not sensitive enough to assess the energy requirements of COMP. Therefore, respiratory gas and power output measures are helpful to provide new information to physiological profile of cross- country cycling.
• An excellent cycling-specific capacity is a prerequisite for successful off-road cycling.
• Data determined from LabT might be utilized to describe semi-specific abilities of MB- athletes on a cycle ergometer, while data originating from COMP might be useful when designing a mountain bike specific training.

Key words: Off-road cycling, mountain biking, oxygen uptake, power output, lactate, heart rate     

Additive Manufacturing-Based In Situ Consolidation of Continuous Carbon Fibre-Reinforced Polycarbonate

Continuous carbon fibre-reinforced thermoplastic composites have convincing anisotropic properties, which can be used to strengthen structural components in a local, variable and efficient way. In this study, an additive manufacturing (AM) process is introduced to fabricate in situ consolidated continuous fibre-reinforced polycarbonate. Specimens with three different nozzle temperatures were in situ consolidated and tested in a three-point bending test. Computed tomography (CT) is used for a detailed analysis of the local material structure and resulting material porosity, thus the results can be put into context with process parameters. In addition, a highly curved test structure was fabricated that demonstrates the limits of the process and dependent fibre strand folding behaviours. These experimental investigations present the potential and the challenges of additive manufacturing-based in situ consolidated continuous fibre-reinforced polycarbonate.     

Changes of Heart Rate Variability After Coronary Bypass Grafting

Background: Heart rate variability (HRV) may serve as a follow-up parameter in patients with coronary artery disease undergoing percutaneous transluminal angioplasty. Several studies have shown significant changes of HRV parameters in the case of restenosis. The value of this method as a prognostic parameter in patients following coronary artery bypass grafting (CABG) is unknown. Methods: In the present study we investigated changes of HRV parameters in patients undergoing CABG to prove whether this method would predict the outcome in these patients. Twenty patients (six female, 14 male, age 51–75 years, mean 62 years) with angiographically documented coronary artery disease (1 × 1-vessel disease, 10 × 2-vessel disease, 9 × 3-vessel disease) were investigated. Eight patients had previous myocardial infarction: 3 × anterior infarction and 5 × inferior infarction. Before and after CABG 24-hour measurement of HRV was performed using Holler monitoring (elapsed time between the two measurements 218 ± 92 days). All patients underwent successful CABG with complete revascularization. The following time domain parameters were calculated: SDNN, SDNN index, SDANN, r-MSSD and pNN50. Results: These parameters showed a significant decrease after CABG (P < 0.05) except rMSSD, which was below the statistic level. The results of the patients without previous myocardial infarction suggested that the parasympathetically influenced paramenters r-MSSD and pNN50 were mainly involved, while in the subgroup with previous myocardial infarction the sympathetically influenced parameters (SDNN, SDANN) were significantly changed. Other variables such as ejection fraction or severity of coronary artery disease did not influence the HRV results. Conclusions: In contratst to patients with revascularization by PTCA, HRV does not seem to be a suitable predictive parameter in patients after successful CABG. Intrinsic operative alterations with injury of cardiac nerves may be responsible for this observation.     

Die Korrektur posttraumatischer Deformitäten am Unterschenkel mit dem „Taylor Spatial Frame“

Objective

Correction of posttraumatic lower leg deformities using percutaneous osteotomy, external fixation with a ring fixator, and computer-assisted gradual correction with the Taylor Spatial Frame (TSF).

Indications

Posttraumatic lower leg deformities not suitable for acute correction and internal fixation or deformities that are suitable but have a significantly increased risk for complications: deformities with poor soft tissue coverage, rigid deformities that require gradual correction, complex mulitplanar deformities, deformities with shortening, and periarticular juvenile deformities.

Contraindications

Posttraumatic lower leg deformities which are suitable for acute correction and internal fixation are also suitable for deformity correction using the TSF. In these cases, however, we recommend acute correction and internal fixation in order to improve the patient comfort. Lack of patient compliance for self-contained correction and pin care.

Surgical technique

Percutaneous fixation of the TSF rings to the main fragments using transosseous K-wires and half pins (hybrid fixation). Percutaneous osteotomy of the tibia either by drilling across both cortices and completion of the osteotomy using an osteotome (DeBastiani method) or by using the Gigli saw with preservation of the periostal envelope. Connection of both rings with six oblique telescopic struts via universal joints (hexapod platform). Computer-assisted planning of the correction.

Postoperative management

Gradual postoperative correction of the deformity by changing the strut lengths according to the correction plan. Strut changes, if required. Osseous consolidation of the osteotomy site with the TSF or revision to internal fixation.

Results

The correction of posttraumatic lower leg deformities using the TSF was performed in 6 cases. The mean deformity was 15° (12–22°) in the frontal plane and 6° (4–8°) in the sagittal plane. The correction time was 19 days (14–22 days). The deviation between planned and achieved correction was 0–3° in the frontal plane and 0–2° in the sagittal plane. The osseous consolidation of the osteotomy site was carried out in the TSF in 5 cases with a mean external fixation time of 112 days (94–134 days). In one case, the TSF was removed after the correction and the osteotomy site was fixed using an intramedullary nail. Pin site infections were observed in 3 cases. There were no further complications. The treatment goal was achieved in all cases. The examination at final follow-up was performed after 1 year. All patients were able to walk without walking aids and with no pain at that time. They were able to perform all of their activities of the daily life and their leisure activities without limitations.