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Biomedical subjects

F Behrens

Publications and source records attributed to F Behrens.

At least 19 recordsLinked to original sources
PubMed1994

Identification of three novel mutations in the CFTR gene using temperature-optimized non-radioactive conditions for SSCP analysis.

Optimal temperature conditions for the detection of 28 known mutations on 15 exons of the human cystic fibrosis transmembrane conductance regulator gene by single strand conformation polymorphism analysis using the Diagen TGGE Apparatus were established. This procedure was applied to the detection of unknown mutations in 58 non-deltaF508 chromosomes. Three novel mutations, -471del3 (5' flanking region), 3171insC (exon 17a) and 4700(T)8/9 (3' non-translated region) of the CFTR gene were found. Mutation 3171insC occurred in conjunction with the delta F508 mutation on the other allele of a child presenting with severe pathology. Mutation -471del3 has so far only been found in one healthy individual and her father, and 4700(T)8/9 is a DNA sequence polymorphism.

Base Sequence↗
PubMed1992

Prevalence of cystic fibrosis mutations in the East German population.

A representative multicenter cystic fibrosis (CF) mutation analysis on about half of all known cystic fibrosis patients of the 5 East German Länder is reported. Analyses for 17 mutations, among them Delta F508, R553X, G542X, S549R,N,I, G551D, S1255X, R347P,H, and Y122X, were performed. As expected, the delta F508 mutation in exon 10 of the CFTR gene is the major gene alteration causing CF in our patients. However, in comparison to studies from Western Germany, a significantly lower percentage of just over 60% is found in our patients, resembling data obtained from slavonic populations. The severe phenotype of cystic fibrosis is most frequently associated with homozygosity for the delta F508 mutation. No particular allele association could be found with the intermediate and mild phenotypes of this disease. The next most frequent of the investigated mutations is R553X (13.3% of non-delta F chromosomes) followed by R347P (9.2%) and G542X (4.4%).

Cystic Fibrosis↗
PubMed1992

An algorithm separating saccadic from nonsaccadic eye movements automatically by use of the acceleration signal.

An algorithm is described to discriminate automatically between saccades and slow eye movements. Sampled data of the eye position have been used to calculate the momentary acceleration of the eye. The higher acceleration values of the saccadic eye movements as opposed to the slow compensatory or pursuit eye movements served to differentiate between the two. The method is demonstrated by search-coil data in squirrel monkeys.

Algorithms↗
PubMed1992

The use of Ender nails in femoral shaft fractures: what are the remaining indications?

The use of Ender nails for the treatment of femoral shaft fractures has been described as technically easier and less time consuming than current intramedullary nailing techniques. We reviewed our results with unlocked Ender nails in 26 stable and 17 unstable fracture patterns an average of 3-4 years after injury. Because of continued instability, 42% of the stable and 76% of the unstable groups required adjunctive stabilization in the form of skeletal traction, a cast, or an external fixator. Additionally, nail migration and shortening and loss of motion at the knee were seen in 14 fractures in each group. Although two thirds of the patients with stable fracture patterns obtained good or excellent results, no outcome in the unstable group was rated excellent and only 19% were considered good. We therefore recommend that rigid locked intramedullary nails be used in femoral diaphyseal injuries. The use of Ender nails should be limited to stable fracture patterns and locked with screws or wires. They may be particularly useful for fractures in femora with small medullary canals (less than or equal to 8 mm), fractures below noncemented femoral prostheses, and fractures in young children requiring intramedullary stabilization without injuring the physeal plates.

Adolescent↗
PubMed1992

Superior dislocation of the fibular head associated with a tibial shaft fracture.

Superior dislocation of the proximal tibiofibular joint occurred in a 34-year-old woman who sustained a Grade 3B open left tibial fracture. An external fixator was applied to the tibia, and the tibiofibular joint was treated by closed reduction. Two bone graftings were performed, and the patient ultimately required a fibular osteotomy to allow tibial impaction. At 10 months posttrauma, the patient is fully weight-bearing and has no pain either at the tibia or the tibiofibular joint.

Adult↗
PubMed1989

Biochemical changes in articular cartilage after joint immobilization by casting or external fixation.

Knees of mature dogs were immobilized for 6 weeks by long-leg casts allowing 8 degrees-15 degrees of motion, a model studied by others, or with external fixators, a new, more severe model that kept the joints rigid. Some animals were allowed to recover for 1 week after the immobilization period. Articular cartilage was examined histologically and biochemically. After 6 weeks of immobilization, water increased 7% in both casted and fixator-immobilized joints compared with normal knee cartilage, while hexuronic acid was 23 and 28% lower, respectively. The limited motion permitted by the casts resulted in a smaller depression of proteoglycan synthesis and less proteoglycan loss during immobilization than occurred in the rigid external fixator group. The protective effect of limited motion was shown clearly during the recovery period: as measured by hexuronic acid content, cartilage from the casted joints had almost recovered within 1 week, whereas the external fixator group experienced little or no recovery during the week after treatment. In contrast to previous studies by others with casted joints, both newly synthesized [35S]sulfate-labeled and accumulated unlabeled proteoglycans from both casted and fixator-immobilized cartilages were able to form complexes with exogenous hyaluronic acid to the same extent as those from control cartilage. Thus, in immobilized cartilage, failure of the newly synthesized proteoglycan to bind to hyaluronate is not a mechanism of accelerated proteoglycan loss. The accelerated proteoglycan turnover appears to be caused by a combination of decreased synthesis and increased proteolysis of the secreted proteoglycans.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

An improved calibration procedure for eye movement recordings in animals using Robinson's electromagnetic scleral search-coil technique.

A method is described to calibrate the eye position signals measured by means of Robinson's electromagnetic scleral search-coil technique in animals which can barely fixate for calibration, e.g. squirrel monkeys, or not at all, e.g. rabbits. Electrical or magnetic interferences superimposed on the search-coil signal can be determined by this method. Consequently, the quality of offset compensation can be tested.

Animals↗
PubMed1989

Open-loop and closed-loop optokinetic nystagmus in squirrel monkeys (Saimiri sciureus) and in man.

Horizontal optokinetic nystagmus (OKN) was measured in 3 normal Squirrel monkeys by means of the electromagnetic search coil technique. Binocular and monocular stimulation of each eye to the left and right by moving vertical stripe patterns of 2.37 or 15 degree period were applied at angular velocities of 0.5 to 400 deg/s. After measurement of horizontal OKN under normal conditions, open-loop OKN gain was determined by monocular stimulation of an eyeball immobilized by means of retrobulbar injections of 11 units botulinum toxin (BoTx type A) and compared with the pre-injection data or with monocular stimulation of the other eye, which remained mobile. In normal Squirrel monkeys gain of optokinetic nystagmus reached values between 0.8 and 0.97 at angular velocities below 1.5 deg/s. Gain under these conditions was related to stimulus angular velocities Vs, i.e. Ge = Ve/Vs. A slightly higher gain was found for binocular than for monocular stimulation. No significant differences were found in OKN when monocular stimulation in the naso-temporal and in the temporo-nasal direction was applied. The upper cut-off angular velocity (-3 dB-point) reached values of 180-230 deg/s, significantly above those observed in man under similar stimulus conditions. Monocular optokinetic stimulation of an immobilized eye led to vigorous optokinetic nystagmus and OKAN of the other eye, whereby maximum gain (Gi = Ve/Vr) was found to be between 20 and 30 at lower retinal stimulus velocities (2-5 deg/s). Gain was related to retinal stimulus velocity Vr. Increase in Vr above 10 deg/s led to a decrease in gain with a slope of about 20 dB per decade. Measurement of gain of closed-loop OKN related to retinal stimulus velocity Vr (which was determined by the difference between Vs and Ve) led to a similar dependence of OKN as in closed-loop stimulus conditions. Differences in sensitivity between the temporal and the nasal visual hemifield stimulation evoking horizontal open-loop OKN are described. Directional selectivity appeared in these experiments. Open-loop OKN data from a human subject are reported. With highly attentive horizontal optokinetic gaze nystagmus, Ve depended on the duration of the pursuit phases of OKN. Ve accelerated with the duration of the individual slow phase of OKN and was reset by each backward saccade (of the covered mobile eye). OKN gain was considerably smaller when the subject intentionally pursued as many stripes as possible of the 1.15 degree period stripe pattern (gain related to Vr about 1.5-3).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

General theory and principles of external fixation.

Starting with a review of the capabilities and main complications of external fixators, this paper shows how advances made during the past two decades have rendered the method safe, reliable, and predictable. Improved component designs, new techniques of pin care, the discovery of three basic concepts that govern the safe and effective application of pin and ring fixators, and the recognition that preoperative and long-term planning are crucial to the success of the method have made external fixation the most adaptable, versatile, and gentle method for stabilizing complex injuries of soft tissue and bone.

Bone Nails↗
PubMed1989

Unilateral external fixation. Methods to increase and reduce frame stiffness.

Unilateral configurations with stiffness characteristics similar to those of the most rigid one- and two-plane bilateral constructs are easily built. Mechanically, most effective were two-plane unilateral frames with a short bone-rod distance. But single- and double-bar anterior unilateral frames had the best combination of clinical and mechanical features. To put gradual frame builddown on a rational basis, a sequence of stepwise frame reduction was developed. This sequence leads from the most rigid unilateral constructs to frames that allow almost complete force transmission across the fracture site while still providing adequate protection against the prevailing sagittal bending moments.

Elasticity↗
PubMed1989

A primer of fixator devices and configurations.

This paper gives a general introduction to the terminology, concepts, and classifications of external fixators. A clear distinction is made between characteristics typical of the three types of external fixators, simple, clamp, and ring, and those typical of the four standard frames that can be built with each of the devices. These four frames, the one-plane unilateral, two-plane unilateral, one-plane bilateral, and two-plane bilateral configurations, differ in the ease of wound access they allow and their mechanical balance, particularly toward bending moments. Hybrids of different devices and frames may prove beneficial for stabilizing complex injuries.

Bone Nails↗
PubMed1988

Use of vancomycin and tobramycin polymethylmethacrylate impregnated beads in the management of chronic osteomyelitis.

Over the past several years there has been a growing interest in the use of locally implanted beads containing antibiotics for the treatment of chronic osteomyelitis. This method has been popularized in Europe and, with few exceptions, gentamicin has been the only antibiotic used. There have been only a few reports from the U.S. and there is little information regarding the pharmacokinetics of antibiotics used in this fashion. To our knowledge this is the first report using vancomycin. Three patients with chronic osteomyelitis were treated with vancomycin and/or tobramycin polymethylmethacrylate beads. These beads were extemporaneously compounded and implanted for up to six weeks. From the site of bead implantation local fluid aliquots were collected for the measurement of antibiotic concentrations. In two patients, initial tobramycin concentrations exceeded 400 mg/L. In one patient receiving vancomycin, initial localized concentrations were approximately 100 mg/L. In all three patients therapeutic concentrations of localized antibiotic were maintained with immeasurable systemic concentrations throughout the period of bead placement. Localized antibiotic therapy for the management of chronic osteomyelitis represents a potential therapeutic alternative to long-term parenteral therapy. Data presented here suggest that other antibiotics, such as vancomycin and tobramycin, can be used successfully in polymethylmethacrylate beads and provide preliminary facts for future investigations of such applications.

Adult↗
PubMed1986

External fixation of the tibia. Basic concepts and prospective evaluation.

External fixation of fractures of the leg may give uneven results and a high rate of complications. We postulate that three basic principles can govern the optimal use of these devices. The external fixation frame should avoid damage to vital anatomical structures, it should allow access to the injured area and it should meet the mechanical demands of the patient and the injury. From 1978 to 1981 these principles were evaluated prospectively in 75 consecutive cases of complex tibial injury treated with an external frame. Most were open fractures. The study confirmed that the principles were safe and effective; they have general application and do not depend on the use of a particular frame or device. By following them we have eliminated the majority of complications seen after traditional methods of external fixation.

Adolescent↗
PubMed1985

Velocity step responses of the human gaze pursuit system. Experiments with sigma-movement.

By means of d.c.-electrooculography or the electromagnetic search coil technique, horizontal and vertical eye position signals were recorded in subjects (head fixed) attentively pursuing a rotating dot circle (dot distance Ps = 0.8 or 1.0 deg). In addition, circular eye pursuit movements were evoked by sigma-movement seen when the stationary dot circle was illuminated stroboscopically (flash frequency fs). The rotation velocity Vs or the velocity of sigma-movement (Ps X fs) was changed in positive or negative steps, leading to acceleration or deceleration of pursuit eye velocity. This step response of eye velocity could be well described by a linear second-order differential equation with an additional dead time of about 80-100 msec. When gaze position error signals were larger than 0.3-0.5 deg, correcting saccades were superimposed on the step response of the smooth pursuit system. Voluntary saccades across the rotating or apparently rotating circle did not lead to any impairment in successive pursuit eye movements or an interruption in the sigma-movement. The gaze tracking command signals (smooth pursuit and saccadic responses) are evidently related to the stimulus movement in the extrapersonal space and not to retinal movement signals.

Adult↗
PubMed1985

Long-term results of displaced talar neck fractures.

Of 36 fractures of the talar neck without comminution of the body, eight were undisplaced, treated closed, and 28 were displaced and treated by open reduction. Twenty of the operations were less than 12 hours after injury. Nineteen of 20 were performed through a medial approach, six with a medial malleolar osteotomy. The long-term results were evaluated by a standard rating system based on classification by the fracture. A protective brace was developed for non-weight-bearing in two patients with complete avascular necrosis, and ankle protection with weight-bearing in ten with partial necrosis. Prompt open reduction and internal fixation, malleolar osteotomy, and protected weight-bearing are recommended in selected cases.

Adolescent↗