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Biomedical subjects

M Hagberg

Publications and source records attributed to M Hagberg.

At least 91 records · Page 5Linked to original sources
PubMed1989

Muscular tenderness evaluated by surface EMG frequency analysis of isometric contractions.

Myoelectric power spectrum analysis was used to compare muscular activity in the masseter and anterior temporal muscles between patients with tender masseter muscles and healthy controls. Surface EMG was recorded for 28 patients and nine controls while they were biting on a bite force transducer during a period of 10-15 s up to maximal effort (100% MVC). The mean frequency (MF) was calculated as a single estimate of the myoelectric power spectrum. Regression analyses of MF's for the masseter muscles versus the force level 0-60% MVC showed significantly less steep slopes of regression for the patients compared interindividually with the controls. As regards the anterior temporal muscles there was no significant difference between groups. One explanation for the difference in MF's for the masseter muscles between patients and controls is that the patients suffered an inhibition or difficulty in recruiting motor units. Different firing rate properties for motor units at high force levels (60-100% MVC) could be one reason for a significantly smaller decrease in MF for the patients' elevator muscles than for the controls.

Adult↗
PubMed1988

Health problems among operators of plastic welding machines and exposure to radiofrequency electromagnetic fields.

To study possible medical effects of high radiofrequency radiation (RF), 113 Swedish men and women were studied by means of a structured interview and rating of subjective symptoms. A test session was included in order to examine coordination and muscular function of the hands. A neurological test concerning two-point discrimination (2-PD) was also done. As referents, 23 women, sewing machine operators and assembly workers, were chosen, interviewed and likewise tested. Exposure measurements were taken of the RF fields around the welding machines. The present Swedish ceiling value of 250 W/m2 for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, both for electric and magnetic fields, were found near machines used in factories for ready-made clothing, which gave a high exposure to the hands. Irritative eye symptoms were reported by 23% of the men and 40% of the women. A group of 27 persons was selected for a clinical eye examination and checked by photographs, and nine persons had modest conjunctivitis. A high prevalence of numbness in hands, especially among women, was found. A significantly impaired 2-PD was found in the exposed women as compared to the referent group. The pregnancy outcome for 305 female plastic welders during 1974-1984 did not show any significant differences with the Swedish average concerning malformation or prenatal mortality.

Adult↗
PubMed1988

Surface EMG frequency dependence on force in the masseter and the anterior temporal muscles.

Myoelectric power spectrum analysis was used to study isometric contractions, 10-15 s long, of the masseter muscles and the anterior temporal muscles. Surface EMG activity was recorded from these muscles for nine females while biting on a bite force transducer up to maximal effort (100% maximal voluntary contraction; MVC). The mean frequency (MF) was calculated as a single estimate of the myoelectric power spectrum. Regression analyses were made of MF versus bite force (0-100% MVC). The mean MF values of all females' masseter muscles increased up to 55-60% MVC. For the anterior temporal muscles no increase in mean MF was found above 20-25% MVC. The increase in MF was possibly dependent on recruitment of type I fibers and low-pass tissue filtering effects. The slope of regression for the force level 0-60% MVC was intraindividually steeper for the masseter muscles than for the anterior temporal muscles. A similar decrease in mean MF was found for the masseter muscles and the anterior temporal muscles for the force level 60-100% MVC. The possibility of muscular fatigue was discussed.

Adult↗
PubMed1988

Antibody-dependent cell-mediated cytotoxicity against Tamm-Horsfall protein in acute pyelonephritis.

The cytotoxic activity of leukocytes from humans and rats with pyelonephritis were examined in an antibody-dependent cell-mediated cytotoxicity assay (ADCC) with CrCl3-treated erythrocytes coated with Tamm-Horsfall (TH) as target cells. The specificity of the ADCC was confirmed by absorption with TH urinary glycoprotein and inhibition of the ADCC activity seen with polyclonal rabbit anti-TH antisera by monoclonal mouse antibodies. The ADCC activity detected in children with acute pyelonephritis was low in the initial phase of the disease, but increased significantly 9 days after the start of antibacterial treatment. In rats with experimental pyelonephritis, ADCC activity decreased significantly with increased duration of infection. Depletion of cells adhering to carbonyl iron led to higher ADCC activity. During the course of the infection the difference in ADCC activity between effector cell preparations depleted using carbonyl iron and those not depleted decreased. The decreased ADCC activity demonstrated during acute pyelonephritis may point to mechanisms operating to diminish the risk of tissue damage.

Acute Disease↗
PubMed1987

Effects of maternal anemia on cardiac output, systemic oxygen consumption, and regional blood flow in pregnant sheep.

We measured regional blood flows and cardiac output and calculated regional oxygen deliveries (blood flow X arterial blood oxygen concentration) and systemic oxygen delivery, oxygen extraction, and oxygen consumption as maternal hematocrit was varied randomly between 31% and 8% by exchange transfusion with plasma or packed sheep red blood cells. We observed three patterns of response: In the heart, brain, and adrenal glands, oxygen delivery was constant or nearly constant over the range of hematocrits studied; in the kidneys, splanchnic organs, and uteroplacental tissues, oxygen delivery was a linear function of hematocrit; in the carcass tissues, oxygen delivery decreased slowly as hematocrits were reduced from 31% to 15% and dropped rapidly at hematocrits less than or equal to 15%. Systemic oxygen consumption was maintained at normal levels, despite reductions in hematocrit to about 15%, because oxygen extraction increased as compensation. At lower hematocrits, systemic oxygen consumption fell in association with a metabolic acidemia, suggesting that, with this severity of acute anemia, oxygen supply to some tissues in the pregnant sheep was inadequate for tissue metabolic demands.

Anemia↗
PubMed1987

Work-related shoulder-neck complaints in industry: a pilot study.

Twenty-six industrial workers, selected from employment records, were examined with a questionnaire, anthropometric measures, muscle strength measurements and filming during work cycles to study the influence of ergonomic factors on shoulder-neck complaints. No differences were observed when comparing age or anthropometric measurements between the nine workers with and the 17 without shoulder-neck complaints. Significantly weaker shoulder muscles were found in workers with shoulder-neck complaints than in those without. A higher median strain on the shoulders in the working situation of workers with shoulder-neck complaints than in the group with no complaints was suggested from the results of a biomechanical analysis of the different work tasks.

Absenteeism↗
PubMed1987

Prevalence rates and odds ratios of shoulder-neck diseases in different occupational groups.

The aim of the present study was to evaluate the association and impact of occupational exposure and diseases of the shoulder and neck. Prevalence rates, odds ratios, aetiological fractions, and their confidence intervals were computed for pooled and non-pooled data of previous published reports. By comparison with office workers and farmers, dentists had an increased odds ratio for cervical spondylosis (two studies) and for shoulder joint osteoarthrosis. Meat carriers, miners, and "heavy workers" also had significantly higher rates of cervical spondylosis compared with referents. Compared with iron foundry workers, civil servants had a significant odds ratio (4.8) of cervical disc disease and a 0.79 aetiological fraction. Whether this was due to exposure or healthy worker effect was not clear. In four occupational groups with high shoulder-neck load an odds ratio of 4.0 was found for thoracic outlet syndrome with an aetiological fraction of 0.75. Rotator cuff tendinitis in occupational groups with work at shoulder level (two studies) showed an odds ratio of 11 and an aetiological fraction of 0.91. Keyboard operators had an odds ratio of 3.0 for tension neck syndrome (five studies). Unfortunately, owing to the scanty description of the work task, the exposure could be analysed only by job title. Examination of published reports shows clearly that certain job titles are associated with shoulder-neck disorders. High rates and aetiological fractions for rotator cuff tendinitis and tension neck syndrome suggest that preventive measures could be effective. Although job descriptions are brief, the associations noted suggest that highly repetitive shoulder muscle contractions, static contractions, and work at shoulder level are hazardous exposure factors. In reports of cross sectional studies of occupational shoulder-neck disorders presentation of age, exposure, and effect distribution may help for future meta-analysis.

Adult↗
PubMed1987

Shoulder muscle strength, endurance and electromyographic fatigue in ankylosing spondylitis.

Shoulder muscle performance was tested in 8 working ankylosing spondylitis (AS) patients and compared with 10 healthy male referents. The AS patients were all in a non-active state and had no shoulder symptoms. Electromyographic fatigue development in the descending part of the trapezius muscle was significantly faster in the AS group during an endurance time test than in the referents. This indicates a change in muscle function consistent with previous reports of myopathy in AS patients. There were no significant differences in shoulder forward flexion strength, endurance time or recovery of endurance time between the AS patients and the referents.

Adult↗
PubMed1986

Exposure to welding fumes and chronic renal diseases, a negative case-referent study.

It was observed that some patients with glomerulonephritis or interstitial nephritis were welders. A hypothesis that welding fumes were an occupational hazard was put forward and initiated the following case-referent study. 143 cases were defined as living males, age 25 to 65 years, with renal disease which caused renal biopsy from 1976-1982. Three population-based referents for each case were selected from the national register of the total population matched by sex, age and community. Exposure was assessed by means of a questionnaire. Only 7% of the cases and 12% of the referents did not answer the questionnaire. There were no differences in exposure rates between cases and referents, even if exposure restrictions were applied. The power of the case-referent study was high.

Adult↗
PubMed1986

Discomfort and bite force in painful masseter muscles after intramuscular injections of local anesthetic and saline solution.

Thirty women with a history of daily pain in the masseter muscles were injected with either lidocaine or saline. The participants were told that they were being given an anesthetic injection to reduce their muscular discomfort. The dentist performing the injections did not know which fluid was used. The discomfort in the masseter muscle was assessed by using Borg's new rating scale before and 10 minutes after injection. The evaluation was followed up on day 1, day 3, and day 7. Bite force was registered between the first molars on the injection side. When scale values were compared individually within groups before and after injection, a significant decrease in discomfort was found in both groups, with the exception of day 1 for the lidocaine group and days 1 and 3 in the saline group. The total lidocaine and saline groups assessed the discomfort similarly except on day 3 when the lidocaine group showed significantly less discomfort. The intraindividual force values increased significantly after injection in the saline group. This effect was not found in the lidocaine group. Despite the minor tendencies for lidocaine to have a better effect, the placebo effect was considered to be high and important.

Adolescent↗
PubMed1985

Regression analysis of electromyographic activity of masticatory muscles versus bite force.

Electromyographic (EMG) activity of the superficial masseter and the anterior temporal muscles versus the bite force was studied in 10 young women. They were fully dentate and had no dysfunction of the stomatognathic system. The descending part of the trapezius muscle was also chosen for EMG registration. The average bite force between the first molars was 396 N (Newton). Steeper slopes for the EMG versus force regression curve at high contraction levels than at low contraction levels for the superficial masseter muscle may indicate that this muscle has a recruitment pattern that differs from that of the anterior temporal muscle. In the case of the anterior temporal muscle there was no difference between the slopes for the EMG-force regression at low and high contraction levels. There was significantly increased activity in the descending part of the trapezius muscle mainly during high bite force levels in half the subjects.

Adult↗
PubMed1985

Irritative complaints, carboxyhemoglobin increase and minor ventilatory function changes due to exposure to chain-saw exhaust.

Complaints of irritation in the eyes, nose and throat as well as dyspnea during work prompted this study to determine whether chain-saw exhaust produces acute exposure effects in loggers. Interviews concerning respiratory symptoms and rating of complaints were conducted for 211 loggers at industrial health care centers. Measurements of carboxyhemoglobin, spirometry and exposure to hydrocarbons, carbon monoxide and aldehydes were assessed for 23 loggers over 36 work periods lasting 2 h each. The prevalence of chronic bronchitis among the 211 loggers was 6%. Irritative complaints of eyes, nose and throat were common and significantly higher than in a reference group. The exposure levels were all below established threshold limit levels, except for carbon monoxide. There was a significant correlation between carbon monoxide exposure and blood carboxyhemoglobin levels. A small but significant decrease of FEV1% and FEF 25-75% during the work periods indicated minimal broncho-constriction, possibly mediated through a reflex mechanism due to irritation of upper airways.

Adolescent↗
PubMed1984

Occupational musculoskeletal stress and disorders of the neck and shoulder: a review of possible pathophysiology.

Disorders and complaints in the neck and shoulder regions are common among industrial workers and are often attributed to occupational musculoskeletal stress. The possible pathophysiological mechanism of occupational stress on the neck and shoulders is reviewed. A mechanical origin for cervical disc degeneration and osteoarthrosis is reported for a few occupational groups. However, a mechanical origin for osteoarthrosis is debatable. A work posture involving elevated arms may accelerate degeneration of shoulder tendons through impairment of circulation due to static tension and humeral compression against the coracoacromial arch. Furthermore, work tasks with repetitive arm movements may evoke shoulder tendinitis or tendo-vaginitis, probably due to friction. Three possible routes to neck-shoulder muscular pain are discussed; mechanical failure, local ischemia and energy metabolism disturbance.

Bone Diseases↗