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Biomedical subjects

M Krogsgaard

Publications and source records attributed to M Krogsgaard.

13 recordsLinked to original sources
PubMed2006

The effect of protein and carbohydrate supplementation on strength training outcome of rehabilitation in ACL patients.

Patients with anterior cruciate ligament (ACL) injury experience atrophy and weakening of the extensor as well as the hamstrings muscles at the injured leg. Especially, the weakness of the quadriceps muscle has been ascribed to hamper daily physical tasks. The purpose of the present study was therefore to investigate if nutrient supplementation during 12 weeks of conservative rehabilitation strength training could enhance hypertrophy and strength of the quadriceps muscle in ACL-injured patients. Twenty-six ACL-injured men and women were included and randomly distributed into three supplementation groups: Protein+Carbohydrate (PC), Isocaloric-Carbohydrate (IC), or Placebo (PL), ingesting the supplementation immediately after each of 36 training sessions. Determined from images of thigh cross-sections (magnetic resonance imaging) the hypertrophy of the quadriceps muscle differed significantly between groups at the distal part, with the PC group demonstrating the largest hypertrophy. Peak torque of the quadriceps muscle at constant velocity 60 degrees.s-1 was significantly elevated in the PC group only, and the time to reach peak torque tended to decrease as well only in the PC group. The results from this study demonstrate that restoration of the distal vasti muscle mass and knee extension muscle strength with resistance training is promoted further by protein-containing nutrient supplementation immediately after single exercise sessions. Thus, exercise-related protein supplementation may seem important for surgery-related rehabilitation of skeletal muscle.

Adolescent↗
PubMed2004

Region-specific mechanical properties of the human patella tendon.

The present study investigated the mechanical properties of tendon fascicles from the anterior and posterior human patellar tendon. Collagen fascicles from the anterior and posterior human patellar tendon in healthy young men (mean +/- SD, 29.0 +/- 4.6 yr, n = 6) were tested in a mechanical rig. A stereoscopic microscope equipped with a digital camera recorded elongation. The fascicles were preconditioned five cycles before the failure test based on pilot data on rat tendon fascicle. Human fascicle length increased with repeated cycles (P < 0.05); cycle 5 differed from cycle 1 (P < 0.05), but not cycles 2-4. Peak stress and yield stress were greater for anterior (76.0 +/- 9.5 and 56.6 +/- 10.4 MPa, respectively) than posterior fascicles (38.5 +/- 3.9 and 31.6 +/- 2.9 MPa, respectively), P < 0.05, while yield strain was similar (anterior 6.8 +/- 1.0%, posterior 8.7 +/- 1.4%). Tangent modulus was greater for the anterior (1,231 +/- 188 MPa) than the posterior (583 +/- 122 MPa) fascicles, P < 0.05. In conclusion, tendon fascicles from the anterior portion of the human patellar tendon in young men displayed considerably greater peak and yield stress and tangent modulus compared with the posterior portion of the tendon, indicating region-specific material properties.

Adult↗
PubMed2002

Collagen fibril size and crimp morphology in ruptured and intact Achilles tendons.

The present study examined the hypothesis that collagen fibril diameter and crimp angle in ruptured human Achilles tendons differed from that of intact ones. Tissue samples were obtained from the central core (distal core) and the posterior periphery (distal superficial) at the rupture site, and the proximally intact (proximal superficial) part of the tendon in 10 subjects (38+/-8 years) with a complete tendon rupture. For comparisons corresponding tissue samples were procured from age (38+/-7 years) and gender matched intact Achilles tendons during routine forensic autopsy. The cross-sectional area density and diameter distribution of fibrils were analyzed using stereological techniques of digitized electron microscopy biopsy cross-sections, while crimp angle was measured by the changing banding pattern of collagen fibers when rotated between crossed polars. Nine of 10 persons with tendon ruptures reported that the injury did not occur during exceedingly large forces, and none experienced any symptoms in the days or months prior to the injury. Fibril diameter distribution showed no region-specific differences in either the ruptured or intact tendons for either group. However, in the distal core there were fewer fibrils in the ruptured compared to the intact tendons in 60-150 nm range, P<0.01. Similarly, in the distal superficial portion there were fewer fibrils in the ruptured compared to the intact tendons in the 90-120 nm range, 2P<0.05, while there were no differences in the proximal superficial tendons. Crimp angle did not display any region-specific differences, or any difference between the rupture and intact tendons. In conclusion, these data suggest that although crimp morphology is unchanged there appears to be a site-specific loss of larger fibrils in the core and periphery of the Achilles tendon rupture site. Moreover, the lack of symptoms prior to the rupture suggests that clinical tendinopathy is not an etiological factor in complete tendon ruptures.

Achilles Tendon↗
PubMed2001

Inhibition of dynamic thigh muscle contraction by electrical stimulation of the posterior cruciate ligament in humans.

We investigated the influence of electrical stimulation of the posterior cruciate ligament (PCL) on the motoneuron pool of the thigh muscle during voluntary static and dynamic muscle contraction. The study group comprised nine young men with no history of injury to the knee joints. Multistranded Teflon-insulated stainless-steel wires were inserted into the PCL guided by ultrasound. In three subjects wires were also inserted into the fat pad of the knee. The PCL was electrically stimulated during static, concentric, or eccentric muscle contraction with a constant load of 20% of the maximal voluntary contraction of either the quadriceps or the hamstrings. Electromyographic signals were recorded with bipolar surface electrodes placed over the vastus medialis, rectus femoris, vastus lateralis, biceps femoris caput longum, and semitendinosus muscles. The stimuli consisted of four pulses delivered at 200 HZ; the stimulus amplitude was two to three times the sensory threshold. The electrical stimulation of the PCL inhibited the ongoing muscle activity in both the quadriceps and hamstrings with latencies of 114-150 ms and 99-130 ms, respectively. Stimulation of the fat pad of the knee did not influence the muscle activity. The study suggests that the mechanoreceptors in the PCL are involved in controlling muscle activity during both static and active muscle contractions. The relative long latency of the reflex makes it unlikely that it can serve as a directly protective reflex for the cruciate ligaments.

Adult↗
PubMed2001

Sensorimotor control of knee stability. A review.

Traditionally, the concept of joint stability considered the displacement (or subluxation) of two bones relative to each other as the measurement index, and attributed the preservation of such stability in its physiologic range to the various ligaments associated with the joint. Although the ligaments are indeed the major restraints of any joint, the significant contribution of the musculature toward joint stability had been grossly overlooked or neglected until the last 15 years. The value and importance of muscular activity in that role becomes immediately apparent if one performs even a superficial functional comparison of muscles and ligaments. Ligaments are passive viscoelastic structures, whereas muscles are dynamic viscoelastic organs. The viscoelastic effects of the ligaments are activated and applied strictly upon the geometric and kinematic configuration of the joint traversing through its range of motion according to fixed force-displacement relationships. The musculature, however, can apply passive viscoelastic effects to the joint when not active (passive tone) and variable dynamic viscoelastic effects when contracting under voluntary or reflexive control, and at any desirable point in the range of motion and in response to joint speed, external load, gravity, pain, and so forth, while executing the functional objective of the movement set by the individual. Preservation of joint stability cannot be ascribed to the ligaments alone, but should be considered as a synergistic function in which bones, joint capsules, ligaments, muscles, tendons, and sensory receptors and their spinal and cortical neural projects and connections function in harmony. The objective of this report is to first review the anatomy and physiology of the various mechanoreceptors and their neural pathways about the joint, and describe some of the current concepts of the reflex arcs elicited by such receptors, with special emphasis on biomechanical outcomes relative to stability. The role of the musculature in maintaining stability while controlling joint motion is then reviewed, with data obtained from experiments performed on humans and animals. Finally, some clinical findings from patients with anterior cruciate ligament deficiency using a brace that simulates the ligament-muscle functions is described.

Anterior Cruciate Ligament Injuries↗
PubMed2001

Is proprioception altered during loaded knee extension shortly after ACL rupture?

Knee joint angle reproduction was measured without loading of the quadriceps and during concentric quadriceps contractions at 20% of maximal voluntary contraction. The threshold of movement detection was measured. The reproducibility of the methods and the effect of an acute ACL rupture < 10 wks post-injury were examined. A test-retest protocol with a 1 wk hiatus was conducted on 15 healthy subjects. Side-to-side differences were tested in 10 patients with acute ACL rupture. The test-retest protocol did not show any significant differences and yielded correlations of r=0.7-0.9 (p<0.01) and coefficients of variations of 5.7-13.0%. No side-to-side differences were detected in the ACL subjects. Quadriceps loaded; injured 3.96 +/- 2.21 , uninjured 4.7 +/- 1.23, unloaded; injured 2.85 +/- 0.56 degrees, uninjured 2.92+/-1.20 degrees. Threshold of movement detection; injured 1.48+/-0.81 degrees, uninjured 1.44+/-0.65 degrees. Therefore, it may be questioned if the ACL itself plays a major role in proprioception performance as it is commonly measured in the laboratory.

Adult↗
PubMed2000

Visualization of myelin basic protein (MBP) T cell epitopes in multiple sclerosis lesions using a monoclonal antibody specific for the human histocompatibility leukocyte antigen (HLA)-DR2-MBP 85-99 complex.

Susceptibility to multiple sclerosis (MS) is associated with the human histocompatibility leukocyte antigen (HLA)-DR2 haplotype, suggesting that major histocompatibility complex class II-restricted presentation of central nervous system-derived antigens is important in the disease process. Antibodies specific for defined HLA-DR2-peptide complexes may therefore be valuable tools for studying antigen presentation in MS. We have used phage display technology to select HLA-DR2-peptide-specific antibodies from HLA-DR2-transgenic mice immunized with HLA-DR2 molecules complexed with an immunodominant myelin basic protein (MBP) peptide (residues 85-99). Detailed characterization of one clone (MK16) demonstrated that both DR2 and the MBP peptide were required for recognition. Furthermore, MK16 labeled intra- and extracellular HLA-DR2-MBP peptide complexes when antigen-presenting cells (APCs) were pulsed with recombinant MBP. In addition, MK16 inhibited interleukin 2 secretion by two transfectants that expressed human MBP-specific T cell receptors. Analysis of the structural requirement for MK16 binding demonstrated that the two major HLA-DR2 anchor residues of MBP 85-99 and the COOH-terminal part of the peptide, in particular residues Val-96, Pro-98, and Arg-99, were important for binding. Based on these results, the antibody was used to determine if the HLA-DR2-MBP peptide complex is presented in MS lesions. The antibody stained APCs in MS lesions, in particular microglia/macrophages but also in some cases hypertrophic astrocytes. Staining of APCs was only observed in MS cases with the HLA-DR2 haplotype but not in cases that carried other haplotypes. These results demonstrate that HLA-DR2 molecules in MS lesions present a myelin-derived self-peptide and suggest that microglia/macrophages rather than astrocytes are the predominant APCs in these lesions.

Amino Acid Sequence↗
PubMed2000

In vivo studies of peritendinous tissue in exercise.

Soft tissue injury of tendons represents a major problem within sports medicine. Although several animal and cell culture studies have addressed this, human experiments have been limited in their ability to follow changes in specific tissue directly in response to interventions. Recently, methods have allowed for in vivo determination of tissue concentrations and release rates of substances involved in metabolism, inflammation and collagen synthesis, together with the measurement of tissue blood flow and oxygenation in the peritendinous region around the Achilles tendon in humans during exercise. It can be demonstrated that this region experiences an increase in blood flow during both static and dynamic exercise, and that exercise causes increased metabolic activity, accumulation of inflammatory mediators (prostaglandins) and increased formation of collagen type I in response to acute exercise. This coincides with a surprisingly marked drop in tissue pressure during contraction. With regards to both circulation, metabolism and collagen formation, peritendinous tissue represents a dynamic, responsive region that adapts markedly to acute muscular activity.

Achilles Tendon↗
PubMed1999

Recombinant antibodies with the antigen-specific, MHC restricted specificity of T cells: novel reagents for basic and clinical investigations and immunotherapy.

MHC class I and II molecules play a central role in the immune response against a variety of invading microorganisms and cells that have undergone malignant transformation by shaping the T cell repertoire in the thymus and by presenting peptide antigens from endogenous and exogenous antigens in the periphery to CD8+ cytotoxic T cells and CD4+ helper T cells. In certain situations MHC-peptide complexes may, however, also initiate and perpetuate an autoimmune attack mediated by autoaggressive T cells leading to diseases such as insulin dependent diabetes mellitus (IDDM), rheumatoid arthritis (RA) and multiple sclerosis (MS). Such MHC-peptide complexes are a desirable target for novel approaches in immunotherapy. Targeted delivery of toxins or other cytotoxic drugs to cells which express specific MHC-peptide complexes that are involved in the immune response against cancer or viral infections and specific masking of MHC-peptide complexes that are involved in autoimmune reactions would allow for a specific immunotherapeutic treatment of these diseases. We have recently demonstrated that antibodies with the antigen-specific, MHC restricted specificity of T cells can be readily generated by taking advantage of the selection power of phage display technology.

Antibodies, Monoclonal↗
PubMed1998

The value of ultrasonography in the diagnosis of labral lesions in patients with anterior shoulder dislocation.

OBJECTIVE: To evaluate the ability of ultrasonography to detect labral lesions in patients with anterior shoulder dislocation. METHODS: We examined 29 patients with anterior shoulder dislocation with ultrasonography prior to arthroscopy. RESULTS: Twenty-six patients had labral lesions diagnosed by arthroscopy. These lesions were detected by ultrasonography with a sensitivity of 88% and a specificity of 67%. All lesions affected the anterior labrum, while six extended to the posterior labrum. The latter were not visualized by ultrasonography. CONCLUSION: Ultrasonography is valuable in the detection of anterior labral lesions even in patients with recent shoulder dislocation.

Adolescent↗
PubMed1994

Collagen turnover after tibial fractures.

Collagen turnover after tibial fractures was examined in 16 patients with fracture of the tibial diaphysis and in 8 patients with fracture in the tibial condyle area by measuring sequential changes in serological markers of turnover of types I and III collagen for up to 26 weeks after fracture. The markers were the carboxy-terminal extension peptide of type I procollagen (PICP), the amino-terminal extension peptide of type III procollagen (PIIINP), and the pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen (ICTP). The latter is a new serum marker of degradation of type I collagen. A group comparison showed characteristic sequential changes in the turnover of types I and III collagen in fractures of the tibial diaphysis and tibial condyles. The turnover of type III collagen reached a maximum after 2 weeks in both groups. The synthesis of type I collagen reached a maximum after 2 weeks in the diaphyseal fractures and after 6 weeks in the condylar fractures. The degradation of type I collagen increased after 4 days and reached a maximum at 2 weeks in both groups. The interindividual variation was wide. On a group basis, the turnover of types I and III collagen had levelled of within 26 weeks, although some patients had clearly elevated parameters at the end of the observational period. We suggest that delayed healing of tibial diaphyseal fractures is accompanied by an early increase in the turnover of types I and III collagen.

Adult↗