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Biomedical subjects

W Herzog

Publications and source records attributed to W Herzog.

At least 19 recordsLinked to original sources
PubMed1999

[Differential diagnosis in anorexia nervosa: glycogenosis II (the Pompe type)].

HISTORY AND ADMISSION FINDINGS: A 29-year-old woman had since early childhood been smaller and thinner than her contemporaries. Her weight was now 36.5 kg, height 158 cm. Anorexia nervosa being suspected she was to be admitted to a psychosomatic clinic. A few days before the date she developed respiratory failure which required mechanical ventilation for a month. Physical examination revealed markedly reduced musculature. INVESTIGATIONS: Muscle biopsy and fibroblast culture indicated acid maltase deficiency (glycogen storage disease Type II [Pompe's disease]). Lung functions were markedly reduced, blood gas analysis revealing global respiratory insufficiency. TREATMENT AND COURSE: Intermittent patient-controlled ventilation (at night by intermittent positive pressure ventilation) clearly improved both her general condition and blood gases. CONCLUSIONS: Acid maltase deficiency should be included as a possible cause of the differential diagnosis of anorexia nervosa. This diagnosis should strictly follow the criteria listed in ICD-10 (International Classification of Diseases), but also after exclusion of other causes.

Adult↗
PubMed1999

Electromyographic responses of back and limb muscles associated with spinal manipulative therapy.

STUDY DESIGN: Ten young, asymptomatic male subjects underwent 11 clinically relevant spinal manipulative treatments along the length of the spine to test the magnitude and extent of reflex responses associated with the treatments. OBJECTIVES: To determine the magnitude and extent of reflex responses elicited by spinal manipulative treatments. SUMMARY OF BACKGROUND DATA: Spinal manipulative treatments have been associated with a reflexogenic relief of pain and a loss of hypertonicity in muscles within the treatment area. However, there is no study in which results show the probability of occurrence or the extent of reflex responses during spinal manipulative treatments. METHODS: Asymptomatic subjects received spinal manipulative treatments on the cervical, thoracic, and lumbar levels and on the sacroiliac joint. Reflex activities were measured using 16 pairs of bipolar surface electrodes placed on the back and proximal limb musculature. The percentage of occurrence and the extent of reflex responses in the back and proximal limb musculature were determined. RESULTS: Each treatment produced consistent reflex responses in a target-specific area. The reflex responses occurred within 50-200 msec after the onset of the treatment thrust and lasted for approximately 100-400 msec. The responses were probably of multireceptor origin and were elicited asynchronously. CONCLUSIONS: This is the first study in which results show a consistent reflex response associated with spinal manipulative treatments. Because reflex pathways are evoked systematically during spinal manipulative treatment, there is a distinct possibility that these responses may cause some of the clinically observed beneficial effects, such as a reduction in pain and a decrease in hypertonicity of muscles.

Adult↗
PubMed1999

Effects of local heparin administration on coronary thrombin activity during percutaneous transluminal coronary angioplasty.

Simultaneously obtained blood samples from the coronary sinus and systemic arterial circulation were analyzed for antithrombin III (ATIII) activity and fibrinopeptide A (FpA) concentration in nine patients undergoing elective PTCA in order to determine the effects of locally delivered heparin. Samples were obtained at the following designated times: prior to the administration of systemic heparin (period I); 5 min following a loading dose of systemic heparin (period II); 5 min following the final balloon inflation but prior to local delivery (period III); and 5 min following the administration of 4,000 units of unfractionated heparin using a local delivery catheter system (period IV). We found consistent increases in both systemic arterial (P = 0.006) and coronary sinus (P = 0.0002) ATIII activity with systemic heparinization designed to prolong the activated clotting time to 300 sec. However, local delivery of heparin further increased coronary sinus ATIII activity (P = 0.003, period III vs. period IV). FpA concentration decreased in both systemic arterial (P < 0.0001) and coronary sinus (P < 0. 0001) samples following systemic heparinization. Moreover, local delivery of heparin further decreased coronary sinus FpA concentration (P = 0.04). Thus, on a background of intense anticoagulation during PTCA, the local delivery of 4,000 units of unfractionated heparin confers incremental antithrombotic activity. Cathet. Cardiovasc. Intervent. 48:84-88, 1999.

Angioplasty, Balloon, Coronary↗
PubMed1999

Modelling of location- and time-dependent deformation of chondrocytes during cartilage loading.

Experimental evidence suggests that the biosynthetic activity of chondrocytes is regulated primarily by the mechanical environment. In order to study the mechanisms underlying remodeling, adaptation, and degeneration of articular cartilage in a joint subjected to changing loads, it is important to know the time-dependent fluid pressure and stress-strain state in chondrocytes. The purpose of the present study was to develop a theoretical model to simulate the mechanical behaviour of articular cartilage and to describe the time-dependent stress-strain state and fluid pressure distribution in chondrocytes during cartilage deformation. It was assumed that the volume occupied by the chondrocytes is small and that cartilage can be treated as a macroscopically homogenized material with effective material properties which depend on the material properties of the cells and matrix and the volumetric fraction of the cells. Model predictions on the time-dependent distribution of fluid pressure and stress and on the time-dependent cell deformation during confined and unconfined compression tests agree with previous theoretical predictions and experimental observations. The proposed model supplies the tools to study the mechanisms of degeneration, adaptation and remodelling of cartilage associated with cell loading and deformation.

Adaptation, Physiological↗
PubMed1999

Modelling concentric contraction of muscle using an improved cross-bridge model.

Despite its overwhelming acceptance in muscle research, the cross-bridge theory does not account for all phenomena observed during muscular contractions. A phenomenon which has received much attention in the biomechanics literature, but has evaded convincing explanation and is not accounted for in the formulation of the classic cross-bridge theory, is the persistent aftereffects of muscular length changes on force production. For example, following muscle shortening, the isometric force of a muscle is depressed for a long time period ( > 5 s) compared to the corresponding isometric force following no length change. In the present study, the classic cross-bridge model was modified in two ways in an attempt to account for the force depressions following muscle shortening. First, the steady-state force depressions following shortening were described by a single scalar variable: the work performed by the muscle during shortening; and second, the dynamic, history-dependent cross-bridge properties were described using a fading memory function. The proposed model was developed and tested for shortening of the cat soleus at constant speeds ranging from 4 to 32 mm/s, for shortening at changing speeds, and for shortening of different magnitudes ranging from 2 to 10 mm. The history-dependent forces during shortening and the steady-state force depressions following shortening were well captured with the modified cross-bridge model. The present model contains two mathematically simple adaptations to the classic cross-bridge model, and is the first such model to account for the long-lasting force depressions following muscle shortening using a single scalar variable.

Actins↗
PubMed1999

The association between negative muscle work and pedaling rate.

The objective of this research was to use a pedal force decomposition approach to quantify the amount of negative muscular crank torque generated by a group of competitive cyclists across a range of pedaling rates. We hypothesized that negative muscular crank torque increases at high pedaling rates as a result of the activation dynamics associated with muscle force development and the need for movement control, and that there is a correlation between negative muscular crank torque and pedaling rate. To test this hypothesis, data were collected during 60, 75, 90, 105 and 120 revolutions per minute (rpm) pedaling at a power output of 260 W. The statistical analysis supported our hypothesis. A significant pedaling rate effect was detected in the average negative muscular crank torque with all pedaling rates significantly different from each other (p < 0.05). There was no negative muscular crank torque generated at 60 rpm and negligible amounts at 75 and 90 rpm. But substantial negative muscular crank torque was generated at the two highest pedaling rates (105 and 120 rpm) that increased with increasing pedaling rates. This result suggested that there is a correlation between negative muscle work and the pedaling rates preferred by cyclists (near 90 rpm), and that the cyclists' ability to effectively accelerate the crank with the working muscles diminishes at high pedaling rates.

Adult↗
PubMed1999

Mechanical load stimulates expression of novel genes in vivo and in vitro in avian flexor tendon cells.

OBJECTIVE: Our experiments were designed to test the hypothesis that tendon cells might respond differently to applied strain in vitro than in vivo. DESIGN: We tested cells in whole tendons from exercised chickens and from isolated surface (TSC) and internal tendon (TIF) in vitro that were subjected to mechanical strain. We hypothesized that tendon cells differentially express genes in response to mechanical loading in vivo and in vitro. METHODS: We utilized an in-vivo exercise model in which chickens were run on a treadmill in an acute loading regime for 1 h 45 min with the balance of time at rest to 6 h total time. Gene expression was analyzed by a differential display technique. In addition, isolated avian flexor digitorum profundus TSC and TIF cells were subjected to cyclic stretching at 1 Hz, 5% average elongation for 6 h, +/- PDGF-BB, IGF-I, TGF-beta 1, PTH, estrogen, PGE2, or no drug and/or no load. mRNA was then collected and samples were subjected to differential display analysis. CONCLUSIONS: Load with or without growth factor and hormone treatments induced expression of novel genes as well as some known genes that were novel to tendon cells. We conclude that the study of gene expression in mechanically loaded cells in vivo and in vitro will lead to the discovery of novel and important marker proteins that may yield clues to positive and negative cell strain responses that are protective under one set of conditions and destructive under another.

Animals↗
PubMed1999

Length dependence of active force production in skeletal muscle.

The sliding filament and cross-bridge theories of muscle contraction provide discrete predictions of the tetanic force-length relationship of skeletal muscle that have been tested experimentally. The active force generated by a maximally activated single fiber (with sarcomere length control) is maximal when the filament overlap is optimized and is proportionally decreased when overlap is diminished. The force-length relationship is a static property of skeletal muscle and, therefore, it does not predict the consequences of dynamic contractions. Changes in sarcomere length during muscle contraction result in modulation of the active force that is not necessarily predicted by the cross-bridge theory. The results of in vivo studies of the force-length relationship suggest that muscles that operate on the ascending limb of the force-length relationship typically function in stretch-shortening cycle contractions, and muscles that operate on the descending limb typically function in shorten-stretch cycle contractions. The joint moments produced by a muscle depend on the moment arm and the sarcomere length of the muscle. Moment arm magnitude also affects the excursion (length change) of a muscle for a given change in joint angle, and the number of sarcomeres arranged in series within a muscle fiber determines the sarcomere length change associated with a given excursion.

Animals↗
PubMed1999

[Quality of life, depression and coping behavior in patients awaiting heart transplant].

From a medical perspective, heart transplantation is now an established procedure for the treatment of patients with terminal heart failure. For the patient involved, it presents itself as a situation of great psychological distress, particularly during the waiting period. In the last few years, this situation has grown worse due to the decline in the number of donor organs and the resulting longer waiting period. The aim of this study was to systematically evaluate this phase of the transplantation procedure in a follow-up study. 52 patients could be assessed in follow-up. Although the patients had already differed from the healthy control group in the areas of depression, quality of life, and physical complaints (p < 0.001) at the beginning of the study, there was a significant increase of depression and a further decline in the reported quality of life in the course of the study. The patients presented themselves as having a low internal and a significantly increased external and fatalistic locus of control. The study stresses the necessity for supportive psychotherapeutic therapy in these patients.

Adaptation, Psychological↗
PubMed1998

Excursion is important in regulating sarcomere number in the growing rabbit tibialis anterior.

1. The mechanical signal(s) that may be important in regulating the number of sarcomeres in series in skeletal muscle fibres or fascicles (sarcomere number) remain(s) speculative, in part because the in vivo mechanical environment of muscle has not yet been defined during sarcomere number perturbations. In the present study, measurements of the in vivo mechanical environment were used to test the hypothesis that increasing muscle excursion results in increased serial sarcomere addition in growing animals. 2. The tibialis anterior (TA) was released from its retinacular restraint at the ankle joint to increase muscle excursion in 4-week-old female New Zealand White rabbits. Twelve weeks post release, muscle excursion and sarcomere number were significantly increased for released TAs compared with control TAs. 3. General cage activity over a 24 h period and in vivo ankle joint kinematics of the experimental leg during hopping on a treadmill were not significantly different between control and release groups, suggesting that altered animal and joint activity patterns were not responsible for the increased serial sarcomere addition associated with TA release. 4. In vivo TA forces during hopping and during a large force-producing foot-flicking motion were significantly decreased in released TAs compared with control TAs. Chronically decreased force production may have been involved in the decreased longitudinal tendon growth observed for the released TA compared with the control TA, which, in turn, may have stimulated the increase in serial sarcomere addition. However, increasing force production of the released TA by partial ablation of the extensor digitorum longus did not inhibit the increase in serial sarcomere addition. 5. The results of this study support the hypothesis that increasing excursion results in increased serial sarcomere addition in growing animals and, when combined with the results of previous studies indicating that decreasing excursion results in decreased serial sarcomere addition, support the working hypothesis that excursion is important in regulating sarcomere number in growing animals.

Animals↗
PubMed1998

Method to assess in vivo knee stability longitudinally in an animal model of ligament injury.

The purpose of this study was to develop a method to prospectively quantify passive knee stability in an animal model of joint injury over time. Knee stability is defined here as the amount of translation or rotation of the tibia relative to the femur for a given application of force or moment, respectively. Five animals that had undergone transection of the anterior cruciate ligament and three control animals that had undergone a sham operation were anaesthetized and positioned in a stereotaxic frame. Motion of the tibia relative to the femur was quantified with use of reflective markers secured to modified bone pins and a three-dimensional motion analysis system. External forces and moments in the transverse plane of the tibia were measured with use of force transducers based on a strain-gauge design. Longitudinal measurements of knee stability were made before either sham surgery (control animals) or transection of the ligament (experimental animals), immediately after surgery, and at 2 and 4 months after transection. The results showed that the animals tolerated the procedures well and that systematic measurements could be obtained. The method described here has the practical advantage over cross-sectional experimental designs in that the number of subjects can be decreased while maintaining statistical power and has the further conceptual advantage that individual changes can be accounted for over time.

Animals↗
PubMed1998

Longitudinal measurement of tibial motion relative to the femur during passive displacements in the cat before and after anterior cruciate ligament transection.

Passive anterior-posterior displacement and medial-lateral rotation of the tibia on the femur in the feline knee were assessed before transection of the anterior cruciate ligament, immediately after transection, and 2 and 4 months after transection. Four anaesthetized experimental and three sham-operated control animals were positioned in a stereotaxic frame. Motions of the tibia relative to the femur were measured with use of 60-Hz video motion analysis, while a strain-gauged system allowed measurement of forces and moments applied to the tibia. Displacement at 15 N of anterior force and 30 degrees of knee flexion increased by an average of 6 mm following transection, and stiffness decreased by an average of 6 N/mm. At 2 and 4 months following transection, there were statistically significant reductions in this abnormal displacement. Stiffness during anterior displacement of the tibia at 30 degrees increased significantly from immediately after transection to 4 months. At 90 degrees, mean anterior displacement decreased from 5.1 mm immediately after transection to 2.9 mm at 4 months. Medial rotation at 30 degrees of knee flexion was significantly decreased from a mean of 16.5 degrees after transection to a mean of 10.7 degrees at 4 months. Changes in medial rotation at 90 degrees, lateral rotation at 90 degrees, and lateral rotation at 30 degrees were not statistically significant. These results indicate a significant change in secondary constraints to tibial motion in response to knee instability.

Animals↗
PubMed1998

[Male anorexia nervosa patients in long-term follow-up].

Despite an increasing number of studies on the long-term course of anorexia nervosa, male patients only play a subordinate role in the majority of investigations. Thus, one section of a more comprehensive study aimed at describing possible differences in the disease course of male and female patients. Total assessment after a mean of 12 years revealed a clearly increased mortality rate of more than 20% in 10 of the male patients examined (as well as 2 male anorexia nervosa patients with an additional physical condition). The male survivors had a better prognosis than the females patients. Male anorectics were in better physical condition than their female counterparts at the time of follow-up. On the Morgan Russell scale, food intake, psychosexual and social state showed a more favorable development in male than in female patients. Male patients had a more favorable course regarding psychosocial integration but a similar course as female patients regarding eating disorder symptoms. The results are discussed theoretically and clinically. Further studies with a larger random selection of patients should be carried out.

Adolescent↗
PubMed1998

[Emotional status of patients on the waiting list for heart transplantation].

Although heart transplantation is by now considered an established procedure in patients with terminal heart failure, there has been a stagnation or even a decline in the number of transplantations performed due to the decreased willingness of the public to provide organs. As a consequence of this development patients have to wait for a donor organ for a much larger time. The aim of this study was to examine patients especially during this very stressful period. From July 1995 to February 1997, 62 patients who had been continuously added to the waiting list were examined regarding their quality of life and emotional state. Completely assessed were 53 patients (participation rate: 85%). As compared to a healthy control group, patients with terminal heart failure on the waiting list reported their quality of life in the physical as well as the psychological area as significantly lower (p < 0.001). The areas of depression (p < 0.001) and anxiety (p < 0.001) also showed a significant difference. There was an obvious correlation (p < 0.01) between the key symptom of terminal heart failure-- dyspnoea--and the measured level of depression. This served to support the notion that there is a connection between the psychological and the somatic state in these severely ill patients. These results point to the necessity of supportive psychotherapeutic treatment during this very stressful time.

Adult↗
PubMed1998

Quantification of in vivo patellofemoral contact forces before and after ACL transection.

Altered knee loading following anterior cruciate ligament (ACL) transection is believed to play an important role in initiating cartilage degeneration. Changes of in vivo joint contact forces pre- and post-ACL transection have not been quantified to date. Consequently, it is not known how knee loading changes following ACL transection, and how it contributes to cartilage degeneration. The objective of this study was to quantify in vivo patellofemoral contact forces in the cat knee prior to and up to nine days following uni-lateral ACL transection. Patellofemoral contact forces were predicted using a planar three-force model with knee extensor forces and patellofemoral geometry as input. Patellofemoral movements were expressed as functions of external knee kinematics. Kinematics and knee extensor forces were measured in both hindlimbs before and after ACL transection during unrestrained locomotion. Following ACL transection, resultant patellofemoral contact forces were decreased by approximately 30% in the ACL-deficient hindlimbs. These results suggest that decreased loading in the ACL-deficient knees may initiate the early degenerative changes observed in cartilage of ACL-transected animals. It remains to be shown, if the general unloading of the joint also results in locally decreased contact loads and altered joint kinematics. Alterations of in vivo patellofemoral loading following ACL transection have been quantified for the first time in this study. A next step will be to quantify the dynamic in vivo cartilage stresses in intact and injured knees which may help to elucidate the effects of mechanical stimuli on cartilage metabolism.

Animals↗
PubMed1998

Evaluation of the finite element software ABAQUS for biomechanical modelling of biphasic tissues.

The biphasic cartilage model proposed by Mow et al. (1980) has proven successful to capture the essential mechanical features of articular cartilage. In order to analyse the joint contact mechanics in real, anatomical joints, the cartilage model needs to be implemented into a suitable finite element code to approximate the irregular surface geometries of such joints. However, systematic and extensive evaluation of the capacity of commercial software for modelling the contact mechanics with biphasic cartilage layers has not been made. This research was aimed at evaluating the commercial finite element software ABAQUS for analysing biphasic soft tissues. The solutions obtained using ABAQUS were compared with those obtained using other finite element models and analytical solutions for three numerical tests: an unconfined indentation test, a test with the contact of a spherical cartilage surface with a rigid plate, and an axi-symmetric joint contact test. It was concluded that the biphasic cartilage model can be implemented into the commercial finite element software ABAQUS to analyse practical joint contact problems with biphasic articular cartilage layers.

Animals↗
PubMed1998

In vivo knee joint loading and kinematics before and after ACL transection in an animal model.

Osteoarthritis (OA) is typically diagnosed in humans in its final stage when joint movement becomes painful. Clinical information about the onset and the mechanisms triggering the degenerative responses are virtually non-existent. However, research on animal models of experimental OA shows that joint adaptations associated with the onset of OA can be detected as early as two to four weeks following disruption of the normal joint mechanics. Transection of the anterior cruciate ligament (ACL) has been shown to cause OA-like symptoms in various animal models including the cat. However. the changes in joint loading responsible for the early tissue responses have not been quantified in vivo. Consequently, the relationship between abnormal joint loading and the onset of OA remains unknown. The purpose of this study was to quantify knee loading before and early after ACL transection in the cat. Knee mechanics were assessed by measuring patellar tendon forces, gastrocnemius forces, knee flexor and extensor EMGs, and hindlimb kinematics before and 5, 7, and 9 days following ACL transection in six experimental and two sham-operated animals. The knee mechanics were not affected by sham-surgery but the muscular forces. knee extensor EMGs, and knee range of motion were reduced following ACL transection compared to corresponding pre-intervention values. These results suggest that ACL transection causes a general unloading and changed kinematics of the knee. We speculate that the decrease in loading and the altered kinematics are responsible for the onset of biologic adaptations of the knee. Precise data about the local joint contact mechanics before and after ACL transection are now required to further relate the detailed changes in the knee mechanics to the early joint changes.

Animals↗