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Biomedical subjects

G Jenner

Publications and source records attributed to G Jenner.

14 recordsLinked to original sources
PubMed2005

Signal intensity of MR-images of thigh muscles following acute open- and closed chain kinetic knee extensor exercise - index of muscle use.

Exercise-induced shifts in signal intensity (SI) of magnetic resonance (MR) images were examined to assess indirectly muscle use in closed- and open-chain knee extensor exercises. Eight men performed five sets of 8-12 repetitions in the leg press (LP) and the seated knee extension (KE) exercises at 50, 75 and 100%, respectively of the 5 x 10 repetition maximum (RM) load. Prior to exercise and after each load setting, images of the thigh were obtained. The increase in SI (Delta SI) of the quadriceps at 100% load was greater (P < 0.05) after KE (32.1 +/- 9.0%) than after LP (21.9 +/- 9.2%). Regardless of load, the four individual muscles of the quadriceps showed similar changes in SI after LP. The three vastii muscles showed comparable increases in SI after KE. M. rectus femoris showed greater (P < 0.05) Delta SI than the vastii muscles at 100%. Neither exercise produced increase in SI of mm. semimembranosus, semitendinosus, gracilis or biceps femoris. Mm. adductor magnus and longus showed increased (13.3 +/- 6.5%; P < 0.05) SI after LP, but not after KE, at 100% load. The present data also infer greater involvement of the quadriceps muscle in the open-chain knee extension than in the closed-chain leg press exercise. The results of the current investigation also indicate similar over-all use among the three vastii muscles in LP and KE, but differential m. rectus femoris use between the two exercises. This report extends the merits of the MR imaging technique as an aid to study individual muscle involvement in a particular exercise task.

Exercise↗
PubMed2005

Crystal quality and differential crystal-growth behaviour of three proteins crystallized in gel at high hydrostatic pressure.

Pressure is a non-invasive physical parameter that can be used to control and influence protein crystallization. It is also found that protein crystals of superior quality can be produced in gel. Here, a novel crystallization strategy combining hydrostatic pressure and agarose gel is described. Comparative experiments were conducted on hen and turkey egg-white lysozymes and the plant protein thaumatin. Crystals could be produced under up to 75-100 MPa (lysozymes) and 250 MPa (thaumatin). Several pressure-dependent parameters were determined, which included solubility and supersaturation of the proteins, number, size and morphology of the crystals, and the crystallization volume. Exploration of three-dimensional phase diagrams in which pH and pressure varied identified growth conditions where crystals had largest size and best morphology. As a general trend, nucleation and crystal-growth kinetics are altered and nucleation is always enhanced under pressure. Further, solubility of the lysozymes increases with pressure while that of thaumatin decreases. Likewise, changes in crystallization volumes at high and atmospheric pressure are opposite, being positive for the lysozymes and negative for thaumatin. Crystal quality was estimated by analysis of Bragg reflection profiles and X-ray topographs. While the quality of lysozyme crystals deteriorates as pressure increases, that of thaumatin crystals improves, with more homogeneous crystal morphology suggesting that pressure selectively dissociates ill-formed nuclei. Analysis of the thaumatin structure reveals a less hydrated solvent shell around the protein when pressure increases, with approximately 20% less ordered water molecules in crystals grown at 150 MPa when compared with those grown at atmospheric pressure (0.1 MPa). Noticeably, the altered water distribution is seen in depressurized crystals, indicating that pressure triggers a stable structural alteration on the protein surface while its polypeptide backbone remains essentially unaltered.

Animals↗
PubMed2000

The safety of a resistive home exercise program in patients with recent onset active polymyositis or dermatomyositis.

The objective was to investigate whether a 12-week resistive home exercise program in addition to conventional medical treatment could be safely performed regarding muscle inflammation, muscle function, and quality of life in patients with active polymyositis (PM) or dermatomyositis (DM). Eleven patients diagnosed with active PM or DM were included. Muscle biopsies and Magnetic Resonance Imaging (MRI) of the thighs were performed. Quality of life, function, and subjective global disease impact (SGDI) were assessed and creatine phosphokinase levels (CPK) were analysed. The patients exercised with the exercise program for 15 minutes and took a 15-minute walk five days a week for 12 weeks. After the exercise period there was no sign of increased muscle inflammation. The group showed significantly improved function and quality of life compared to the start of study. It seems that this exercise program safely can be employed in patients with active PM or DM, and we suggest that physical exercise should be included in the rehabilitation of these patients.

Adult↗
PubMed1999

MR imaging of lipoma and liposarcoma.

PURPOSE: To evaluate whether lipoma, atypical lipomatous tumors, and liposarcomas can be differentiated by MR images. MATERIAL AND METHODS: The MR images of 59 lipomatous lesions and liposarcomas were retrospectively reviewed. Apart from size, surgical site, location and margins, the percentage of fat of the tumor volume was assessed as none, 1-75%, 75-95%, or 95-100%. RESULTS: None of the 18 liposarcomas contained fat that could be recognized by MR imaging. The 3 atypical lipomatous tumors all contained fat but less than 75% of the tumor volume. In 32 of 38 ordinary lipomas, the percentage of fat was 95-100%, and in 4 less than 95% of the tumor volume. Two lipomas did not contain fat that could be recognized by MR imaging. CONCLUSION: A lesion which predominantly has a fat signal is, in all probability, an ordinary lipoma. Lesions with less fat, but still mostly fatty, may either be lipoma or atypical lipomatous tumor. In this group, the discrimination between these two entities cannot be based upon imaging features. In the absence of a fat signal, liposarcoma or lipoma cannot be differentiated from other soft tissue tumors.

Adipose Tissue↗
PubMed1999

Effects of high resistance training in patients with myotonic dystrophy.

Nine ambulatory subjects with myotonic dystrophy participated in a supervised 12-week progressive high-resistance training program. Knee extensor muscles were trained 3 times a week with free weights, 3 x 10 repetitions at 80% of 1RM. One leg was randomly chosen for training and the other served as control. Six patients completed the training program. In the trained leg, 1RM increased from 16.4 +/- 3.4 kg to 21.8 +/- 2.6 kg (p = 0.0002). There was no difference between pre- and post-training concentric or eccentric isokinetic values at 30 degrees/second in either leg. Muscle biopsy from m. vastus lateralis in the trained leg revealed no systematic difference in the degree of histopathological abnormalities before and after training. After training, there was a tendency toward increase in cross-sectional area of type I muscle fibres. However, the number of subjects was too small to draw conclusions regarding the effects of training on the histopathological changes. Magnetic resonance imaging revealed no difference in the m. quadriceps area after training. In conclusion, patients with myotonic dystrophy improved their muscle strength without any observed negative side effects after a 12-week high-resistance training program.

Adult↗
PubMed1996

MR imaging of skeletal muscle hemangiomas. A report of 16 cases.

PURPOSE: Our purpose was to evaluate how MR imaging depicts the vascular fibrofatty structure of hemangiomas. MATERIAL AND METHODS: MR images of 16 histologically proven skeletal muscle hemangiomas were reviewed retrospectively in a nonblinded manner. One patient was examined at 0.5 T, 9 at 1.0 T, and 6 at 1.5 T, and the imaging protocols varied. RESULTS: All lesions were lobulated/tubular. Signal characteristics of fat were seen in 13 lesions as lace-like thin septa within or around the tumor. All 16 studies exhibited a hyperintense signal on T2-weighted spin-echo (SE) (n=15) or T1-weighted fast fat suppressed inversion recovery SE images (n=1). Postcontrast images showed marked signal enhancement in parts of the areas, both of high and low T2-weighted signal. Surgical staging based on MR images was correct in all lesions. CONCLUSION: MR images display the characteristic vascular fibrofatty structure of hemangiomas and may allow correct diagnosis.

Adolescent↗
PubMed1994

Changes in magnetic resonance images of muscle depend on exercise intensity and duration, not work.

Echo-planar magnetic resonance imaging was used to study the effect of exercise rate and duration on magnetic resonance imaging signal intensity (SI) of anterior tibialis muscle in normal human subjects (mean age 35 yr, n = 6). Axial midcalf echo-planar images (repetition time/echo time = 6,000/45, acquisition time = 80 ms) were acquired every 6 s for 1 min before and during 15 min of dynamic ankle dorsiflexion exercise (peak force 36% of 1 repetition maximum) at 10, 20, and 30 contractions/min. At each rate, muscle SI rose along an approximately exponential time course (mean time constant 1.8 min) toward a plateau that was linearly dependent on force times contraction rate (r = 0.64, P < 0.01) but varied significantly among subjects. The results confirm previous reports that changes in muscle SI correlate with exercise intensity, but not with total work performed, over a submaximal range of exercise intensities.

Adult↗
PubMed1989

Zinc in the elderly.

Zinc levels in plasma and leucocytes of elderly patients with and without cutaneous ulcers and in hospital were compared with those of a group of healthy elderly living at home and of a younger group. The groups in hospital had lower levels of plasma and leucocyte zinc than the control groups, but these were not associated with cutaneous ulcers. The zinc intake of the patients in hospital was well below the recommended daily allowance. Tissue zinc levels were found to be low in elderly patients in hospital, probably due to poor intake, but their contribution to the formation of skin ulcers was unproven.

Aged↗
PubMedDate not supplied

Rapid MR imaging of the liver: comparison of twelve techniques for single breath-hold whole volume acquisition.

Twelve magnetic resonance imaging pulse sequences for single breath-hold whole volume acquisition of the liver were evaluated on volunteers. Liver and spleen contrast to noise ratio (C/N), overall image quality, and grade of artifacts were compared. The 12 sequences included T2-weighted fast spin echo (FSE) with or without fat suppression (FS), fast multiplanar spoiled gradient recalled imaging (FMPSPGR), fast gradient recalled imaging without preparation pulses (FGR), FGR with inversion recovery preparation pulse nulling the liver or fat (IR-FGR-L and IR-FGR-F), FGR with driven equilibrium preparation pulse (DE-FGR), single shot moderately or heavily T2-weighted spin echo echo planar imaging (SE-EPI-mT2 and SE-EPI-hT2), multi-shot moderately T2-weighted spin echo echo planar imaging (multi-shot SE-EPI-mT2), inversion recovery EPI, and gradient echo EPI. In the quantitative analysis, FSE + FS showed a significantly higher C/N ratio than the others (p < 0.05). In the qualitative evaluation, DE-prepFGR, and single and multi-shot SE-EPI-mT2 had good results, as did FSE and FSE + FS. Further studies should be conducted to determine whether or not these breath-hold sequences can obviate current conventional non-breath-hold sequences.

Adipose Tissue↗
PubMedDate not supplied

Flow velocity and volume measurement of superior and inferior mesenteric artery with cine phase contrast magnetic resonance imaging.

The flow velocity and volume of the superior and inferior mesenteric arteries (SMA, IMA) were measured with cine phase contrast magnetic resonance (MR) imaging in five healthy volunteers. Each volunteer was first measured in a fasting state, and then one, two, and three hours after a meal. The average SMA flow volume of the volunteers was 230.3 +/- 46.8 ml/min (mean +/- standard error) during the fasting state, and 714.7 +/- 207.7 ml/min, 339.2 +/- 85.7 ml/min, and 263.8 +/- 21.0 ml/min, respectively, at one, two, and three hours postmeal. The increase at one hour postmeal was statistically significant (p < 0.05). The corresponding flow measurements in the IMA were 63.1 +/- 11.2 ml/min, 67.6 +/- 11.2 ml/min, 57.9 +/- 8.6 ml/min, and 53.2 +/- 6.8 ml/min. These values do not represent a statistically significant flow volume change in the IMA. In all volunteers, the SMA volumetric flow increased the most one hour after the food challenge (72-400% relative to baseline). Diastolic velocity in the SMA increased significantly one hour postmeal, but systolic velocity did not change significantly. The IMA did not demonstrate a significant change in either systolic or diastolic velocity. The difference between the SMA and IMA in the way of reacting against the food challenge is thought to represent the difference between the requirements of small and large intestine for blood supply after the food challenge. These data demonstrate the possibility of this modality for the assessment of conditions such as chronic mesenteric ischemia.

Adult↗