Biochemical characterization of density-separated human erythrocytes.

A simple, reproducible method for the separation of human erythrocytes, described recently (Murphy, J. R. (1973) J. Lab. Clin. Med. 82, 334-341) has been utilized for the purpose of obtaining a wide range of biochemical data on these cells. Using phthalate ester density centrifugation of the fractions obtained by Murphy's method, we established that the cells were separated exclusively on the basis of their densities. Data on a wide range of biochemical and hematological parameters, when compared with previously reported density separation procedures showed that this simple technique can be used to fractionate the cells according to their densities (age) in their own plasma. Cells of increasing density consistently and reproducibly exhibited an increase in hemoglobin concentration, a moderate elevation in Na+ and a decrease in the following: K+, acetylcholinesterase, sialic acid, membrane protein, 2,3-diphosphoglycerate, ATP, cholesterol, phospholipid, mean corpuscular volume and critical hemolytic volume, However, no change in mean corpuscular hemoglobin was evident. The observed differences were not artifacts of the centrifugation process. This was determined in recentrifuged top fractions from which new top and bottom cells were obtained. The latter cells resembled the top fraction from which they were obtained, rather than the original bottom fraction. Whereas the parameters mentioned above exhibited consistency and reproducibility, such was not the case with the ATPase values. Depending on the cell density group examined and/or buffer as well as other conditions, significant variability in the activity levels of the ouabain sensitive, as well as the Ca2+ -stimulated ATPase, was observed. Use of these enzyme activities as indicators of cell age must be viewed with caution.

Effects of Tris and histidine on human erythrocytes and conditions influencing their mode of action.

1. The incubation of human erythrocytes in 0.172 M Tris - HCl, pH 7.6 buffer at 37 degrees leads to (1) a pronounced cellular volume increase, (2) a preferential release of Na+, and (3) if continued sufficiently long, hemolysis. These effects are pH dependent and also are influenced to a considerable degree by such diverse reagents as NaC glucose, and histidine. In each instance, increasing levels of the latter compounds in a Tris - HCl incubation mixture led to diminished cellular volume increase and prolonged time of onset of hemolysis. 2. Histidine solutions of 0.31 M, pH 7.5 caused a rapid and dramatic decrease in cellular volume of human erythrocytes and a concomitant rapid exit of cations. However, in a prolonged incubation, human erythrocytes slowly regained their cell volume as a result of histidine entry into the cell. Of considerable interest: Tris swollen cells undergo immediate shrinkage to far below the initial cell volume when incubated in histidine at 37 degrees C. Through repetition of this process two additional times, as much as 90-95% of the total cellular Na+ and K+ was removed without hemolysis. 3. Human erythrocytes washed in 0.12 M MgCl2 and then suspended in 0.31 M histidine, pH 7.5, lost upwards of 60% of their total Na+ and 30% of their total K+ after a 40 min incubation at 37 degrees C. However, when increasing amounts of 0.172 M Tris - HCl, pH 7.6 were added to the histidine suspension of cells, the release of K+ was reduced to 5% but the release of Na+ decreased only to 40% of the total cellular level. On the basis of these observations, it is evident that Tris exerts a preferential activity towards the efflux of Na+ from the human erythrocyte, whereas histidine results in high efflux of K+ and Na+ from the cell.

Sensory dysfunction in fibromyalgia patients with implications for pathogenic mechanisms.

This study, addressing etiologic and pathogenic aspects of fibromyalgia (FM), aimed at examining whether sensory abnormalities in FM patients are generalized or confined to areas with spontaneous pain. Ten female FM patients and 10 healthy, age-matched females participated. The patients were asked to rate the intensity of ongoing pain using a visual analogue scale (VAS) at the site of maximal pain, the homologous contralateral site and two homologous sites with no or minimal pain. Quantitative sensory testing was performed for assessment of perception thresholds in these four sites. Von Frey filaments were used to test low-threshold mechanoreceptive function. Pressure pain sensitivity was assessed with a pressure algometer and thermal sensitivity with a Thermotest. In addition the stimulus-response curve of pain intensity as a function of graded nociceptive heat stimulation was studied at the site of maximal pain and at the homologous contralateral site. FM patients had increased sensitivity to non-painful warmth (P < 0.01) over painful sites and a tendency to increased sensitivity to non-painful cold (P < 0.06) at all sites compared to controls, but there was no difference between groups regarding tactile perception thresholds. Compared to controls, patients demonstrated increased sensitivity to pressure pain (P < 0.001), cold pain (P < 0.001) and heat pain (P < 0.02) over all tested sites. The stimulus-response curve was parallely shifted to the left of the curve obtained from controls (P < 0.003). Intragroup comparisons showed that patients had increased sensitivity to pressure pain (P < 0.01) and light touch (P < 0.05) in the site of maximal pain compared to the homologous contralateral site. These findings could be explained in terms of sensitization of primary afferent pathways or as a dysfunction of endogenous systems modulating afferent activity. However, the generalized increase in sensitivity found in FM patients was unrelated to spontaneous pain and thus most likely due to a central nervous system (CNS) dysfunction. The additional hyperphenomena related to spontaneous pain are probably dependent on disinhibition/facilitation of nociceptive afferent input from normal (or ischemic) muscles.

Relation between pain location and disc pathology: a study of pain drawings and CT/discography.

OBJECTIVE: The purpose of this study was to determine whether pain location indicated in pain drawings was related to the specific lumbar disc level(s) that was abnormal in appearance and painful upon discographic injection. DESIGN: Data were collected prospectively. SETTING: This study was conducted in a spine specialty clinic. PATIENTS: The study group consisted of 187 patients (118 men, 69 women; mean age = 37.2 years, range = 18-62 years) with low back pain with or without leg pain. All patients were undergoing computed tomography (CT)/discography at the three lowest lumbar levels for diagnostic purposes. INTERVENTIONS: Pain drawings were completed the day of but prior to undergoing discography. Discographic pain responses were recorded with respect to the similarity to the patient's clinical symptoms. Pain drawings were classified based on the presence or absence of pain in five areas: low back and/or buttocks, posterior thigh, posterior leg, anterior thigh, and anterior leg. The drawings were scored with the system described by Ransford et al. (1976, Spine 1: 127-34), and those likely to be indicative of psychological problems were analyzed separately (n = 43). OUTCOME MEASURES: Results were determined by analyzing the relation between the location of pain in the drawings and the specific lumbar disc level(s) found to be painful and disrupted by discography. RESULTS: There was a significant relation between pain location indicated in the drawing and the lumbar disc level(s) identified as clinically painful and disrupted by CT/discography (p < 0.05, chi-square). Pain limited to the low back and buttocks was frequently associated with the absence of disc pathology (58.3%). When pain in the posterior thigh or leg was present but there was no pain in the anterior drawing, patients frequently had a positive L5-S 1 disc (> or =75%). In patients with anterior thigh pain, with or without posterior thigh or leg pain, the L4-5 disc was frequently symptomatic (>63%). The pattern of no posterior thigh or leg pain but with pain radiating into the leg anteriorly was most commonly associated with the L3-4 disc (71.4%). CONCLUSIONS: The results of this study indicate that pain drawings may be helpful in identifying which specific discs are associated with pain complaints. As with any evaluation, the drawings should be considered in combination with findings from other assessments.

Degree of disc disruption and lower extremity pain.

STUDY DESIGN: Data were collected prospectively from patient-completed pain drawings, lumbar discographic pain responses, and computed tomographic-discographic images. OBJECTIVES: To determine if there were differences in pain location or the type of pain associated with the severity of symptomatic disc disruption. SUMMARY OF BACKGROUND DATA: Lower extremity pain related to spinal pathology was for a long time attributed primarily to nerve root compression. However, this simple model could not explain all lower extremity pain. Other mechanisms such as biochemical agents have been implicated. Also, nerve endings have been found in the outer layers of the anulus. Such endings could be associated with pain referred from the disc into the lower extremities. Pain drawings have been used in several studies to investigate various back pain origins and provide an easily administered method to document pain location. METHODS: Pain drawings were completed by 187 patients undergoing discography at the three lowest levels. The study group consisted of 118 men and 69 women with an average age of 37.2 years (range, 18-62 years). Computed tomographic discograms were scored using the Dallas discogram description, which assigns separate scores for discs with disruption of outer anular fibers (Grade 2) and those with disruption of the outermost anular layers associated with deformation or herniation of the outer anular well (Grade 3). The pain response provoked with each disc injection was recorded as pressure only or painless, pain dissimilar to clinical symptoms, similar to symptoms, or the exact reproduction of clinical pain, in this study, the similar and exact reproduction responses were combined and considered to be "symptomatic." The drawings were classified based on the presence or absence of pain in three regions: low back or buttocks, thigh, and leg. The drawings were also scored using the system described by Ransford, and those that were likely to be indicative of psychological problems were analyzed separately (N = 43). RESULTS: There was no significant difference in the distal location of lower extremity pain among patients whose most severe symptomatic disc disruption was a Grade 2 compared with those with symptomatic Grade 3 disruption (62.2% vs. 61.7%; P > 0.75; chi-square). The figure was similar for patients with both symptomatic Grade 2 and 3 disruption (72.7%). However, patients with symptomatic Grade 2 disruption used significantly more symbols to describe their pain, and in particular aching pain, than did those with symptomatic Grade 3 disruption. CONCLUSIONS: These results indicate that disc disruption passing into the outer layers of the anulus, but not resulting in deformation of the outer anular wall, was as frequently associated with lower extremity pain as were discs with more severe disruption deforming the outer anular wall; however, they were associated with a greater degree of aching pain. These findings support that lower extremity pain may be referred from the disc.

Tibiofemoral joint forces during isokinetic knee extension.

Using a Cybex II, eight healthy male subjects performed isokinetic knee extensions at two different speeds (30 and 180 deg/sec) and two different positions of the resistance pad (proximal and distal). A sagittal plane, biomechanical model was used for calculating the magnitude of the tibiofemoral joint compressive and shear forces. The magnitude of isokinetic knee extending moments was found to be significantly lower with the resistance pad placed proximally on the leg instead of distally. The tibiofemoral compressive force was of the same magnitude as the patellar tendon force, with a maximum of 6300 N or close to 9 times body weight (BW). The tibiofemoral shear force changed direction from being negative (tibia tends to move posteriorly in relation to femur) to a positive magnitude of about 700 N or close to 1 BW, indicating that high forces arise in the ACL when the knee is extended more than 60 degrees. The anteriorly directed shear force was lowered considerably by locating the resistance pad to a proximal position on the leg. This model may be used when it is desirable to control stress on the ACL, e.g., in the rehabilitative period after ACL repairs or reconstructions.

Assessment of jet pilots' upper trapezius load calibrated to maximal voluntary contraction and a standardized load.

Electromyographic (EMG) recording of the myoelectrical activity level in the trapezius muscle is often used as one method of assessing neck and shoulder muscle workload. To analyse how the normalization value influences interpretation of upper trapezius load during a work task, two different reference values for normalization were applied - one obtained during a maximum voluntary contraction (MVE) and the other during a standardized muscular load (RVE). Nine jet pilots (ages 30-48 yr) flew two sorties in a 37 Viggen aircraft using either of two types of head garment while 3-D acceleration and muscular activity were recorded. In each sortie twice in the programme a steep left turn at 5-6 +G(Z) was performed. The highest activity level (MVE) obtained during shoulder elevation combined with an isometric heavy resistance (maximum) against arm flexion/abduction was used as one normalization value. Before, between, and after the two flights, 15 s EMG recordings (RVE) during a dumbbell test in the same arm position were also taken. The muscular activity in the upper trapezius during a given task varied a great deal between individuals, but the reliability of the amplitude levels on different occasions during a work day was good, given the same electrode location and application. If muscular activity during a standardized loading force (e.g. dumbbell test) is used to normalize the recordings for workload assessments related to utilized muscular capacity, a subject with high muscular strength and comparatively low workload might in some situations be assessed as having the same workload as, or a higher load than a subject with less strength and a comparatively high workload. While normalization using a standardized force can be used to assess changes in workload, for assessing workload related to the individual's capacity recording the myoelectrical activity during maximal contraction is preferable.

Factors associated with successful vocational rehabilitation in a Swedish rural area.

The objective of this study was to identify factors associated with a positive outcome of vocational rehabilitation, and to identify groups that have been successfully rehabilitated in a Swedish rural area. In this study vocational rehabilitation is defined as medical multidisciplinary, psychological, social and occupational activities aiming to re-establish, among sick or injured people with previous work history, their working capacity and prerequisites for returning to the labour market. The study was based on 732 people on registered long-term sick-leave who, in a rural area in northern Sweden during 1992-94, became objects for vocational rehabilitation. Bivariate and stepwise logistic regression analysis was used to identify factors associated with the outcome. By successful vocational rehabilitation is meant reporting well (no economical benefit) at all three time-points 6, 12 and 24 months after termination of rehabilitation, or lowered benefit levels. The results indicate that younger, male, employed persons, with an early start on rehabilitation, in a programme entailing education, and partly sick-listed before the start of this programme, had the greatest chance of successful rehabilitation. In contrast, older, female, unemployed people, with a delayed start on rehabilitation, without education, and fully sick-listed before the start, greatly risked being unsuccessful with vocational rehabilitation. The results indicate how to improve the rehabilitation process: several process-related factors shown to be connected with successful vocational rehabilitation include time before the start of rehabilitation, partial instead of full sickness benefit, and education programmes.

Women at work despite ill health: diagnoses and pain before and after personnel support. A prospective study of hospital cleaners/home-help personnel with comparison groups.

The present study sought to elicit the diagnoses behind the pain conditions causing complaints by female hospital cleaners and home-help personnel who were working despite their symptoms. We also wished to describe the prevalence of musculoskeletal diagnoses and the intensity, frequency and location of pain, and changes in the clinical picture and pain after personnel supporting interventions. A prospective study was carried out with intervention groups and non-randomized comparison groups. The hospital cleaners intervention programme comprised occupational organizational measures, competence development, physical and psychosocial working environmental measures and individual and rehabilitation measures on both an individual and a group basis. The home-help programme comprised a 2-week stay at an orthopaedic rehabilitation unit, training of supervisors, comrade massage, purchase of training equipment and stress management. Myalgia/ tendinitis occurred in 61% of shoulder girdle elevators, 18% of rotator cuffs, 16% of dorsal neck muscles and 29% of hip muscles. There was musculoskeletal pain in the lower back in 28% of cases. Referred pain from a musculoskeletal focus occurred in about one-sixth to one-third of individuals with the diagnosis in question. Neurogenic pain occurred in 6% of cases. No fibromyalgia syndrome was found. One-third of individuals felt pain all the time or almost all the time. The mean rated perceived "worst pain" was 70 mm on a visual analogue scale of 1-100 mm. Comparisons between intervention and reference groups indicated that some improvement in the clinical picture can be attained using this kind of general support programme for employees.

Causes of Dependence in Personal Care Three Years after StrokeA Study in the Home Environment.

Many activities of daily living (ADL) assessment instruments are available for judging the ability to perform personal care in, among others, persons suffering a stroke. However, ADL assessment instruments do not normally treat the underlying causes of failure to perform an activity.Seventeen persons with stroke were videotaped when performing personal care in their home environments about three years after the incident. The underlying causes of their failure in personal care are described in intrapersonal, interpersonal, and environmental dimensions. Interpersonal obstacles proved to be the main reasons why the persons in this study did not perform personal care.The self-reports of a 24-hour activity pattern showing the relationship between use of time for performance of personal care, sleep and rest, and other activities are presented.For the participants in this study, the Klein-Bell ADL Scale, an assessment instrument comprising 170 observation points, was judged to be valid and reliable, but some modifications are proposed.

Anatomical, histological, and physiological factors in experienced downhill skiers.

The present investigation was performed in experienced downhill skiers to study anthropometrical and physiological changes. We also studied the muscles that are most active during downhill skiing and the histological properties of these muscles.

Relative mechanical load on ankle and knee muscles during standing manual materials handling-a study of packing work.

The muscular load on the ankle and knee was investigated in 72 different packing work postures. The principle used was as follows; if the load moment about a joint is divided by the counteracting maximum muscular moment, a muscular strength utilization ratio (MUR) is obtained. The MUR was calculated for a large, an average-sized and a small man depending on whether they were all either strong, of mean strength, or weak, thus giving nine MUR values for each posture. Different combinations of box size, box angle, edge height and weight of object handled were studied. The lowest MUR for both the ankle and the knee were obtained in postures with the smallest box angled at 90° to the horizontal, with the upper edge at elbow height or higher. The highest MUR values were with a few exceptions obtained with the largest box angled at 0° or 30° with the upper edge at elbow height or lower.

Shoulder-arm muscular activity and reproducibility in carpenters' work.

The purpose of the present study was to analyse the levels of muscle activity that experienced carpenters reach in some arm-shoulder muscles when performing familiar tasks, and to find whether there are intra- and inter-individual similarities in muscle activity. Ten healthy carpenters performed twice on the same day: their tasks were, manual screwdriving at eye level, manual sawing on a saw horse, and nailing upward into the ceiling. Two weeks later the experiment was repeated. Normalized electromyography was used. The median activity levels during the period analysed did not exceed 15% of maximum electromyographic activity for any of the muscle groups studied. For some muscles and activities there were wide ranges of median activity levels. The most activated muscles in all three tasks were the trapezius pars descendens, infraspinatus and anterior deltoid. There was an intra-individual similarity between the median values from each trial.

Isometric strength in flexors, abductors, and external rotators of the shoulder.

The aim of this study was to map the isometric shoulder muscle strength of 96 men and 90 women randomized from the population register of Stockholm citizens (reference groups), and of 83 male furniture removers and 89 female secretaries (aged 19-65 years, all four groups). Maximum isometric strength of the right-side shoulder flexors (90° joint angle), abductors, and external rotators (0°) was recorded with the subject sitting in a standardized position in an adjustable chair. Women had 43, 55, and 56% of the men's strength in the abductors, flexors, and external rotators respectively. Neither of the female test groups showed any change in maximum isometric strength with increasing age. Men from the reference group showed an age-related difference only in shoulder flexor strength, where the older men (45-65 years) had 89% of the younger men's (19-44 years) strength. The strength values of older furniture removers were 77-83% of the younger colleagues' values in all muscle groups tested. The muscular strength utilization ratio (MUR%) when holding the arm without external load at 90° shoulder flexion was 22-25 MUR% for the male groups and 34 MUR% for the female groups, which shows that the muscular load on the shoulder caused by the weight of the arm is of great importance.

Influence of sitting postures on neck and shoulder e.m.g. during arm-hand work movements.

The aim of the study was to analyze the effect of different sitting postures on the level of activity in some neck and shoulder muscles in a standardized work cycle involving movement of the arm/hand. Ten experienced female workers volunteered in a laboratory study. Full-wave rectified, low-pass filtered, time-averaged and normalized e.m.g. was used. Surface electrodes were applied unilaterally at six locations. The course of the level of muscle activity during the standardized work cycle is presented. There was a tendency to higher level of activity when the arm/hand was moving along the high part of the work object compared to along the low part. The level of activity during the standardized work movement with the arm/hand was significantly influenced by the sitting postures chosen. The highest activity levels were found in the posture with the whole spine flexed. A marked reduction of the level of activity was obtained when a posture with the thoraco-lumbar spine slightly inclined backward was used.

Medical and social factors affecting behaviour patterns in patients with acquired brain damage: a study of patients living at home three years after the incident.

This study aimed to describe the consequence of stroke or brain trauma 3 years after the incident for individuals living at home, and how patterns of behaviour were influenced by determinants. One hundred and eighty-eight individuals in three age groups answered a questionnaire. Answers were classified according to WHO's ICIDH, and 11 areas of behaviour were distinguished. Diagnoses and locations of lesions were noted from medical records. Impairment and disability increased with increasing age at the time of the incident. Individuals working before but not after the incident indicated decreased life satisfaction and changed intellectual function, personal care, and domestic/housework/gardening activities, and inability to organize their time. Those who had resumed work but at different tasks indicated changed emotional and sensorimotor function and content in leisure activities. The influence of the localization and lateralization of the lesion is also discussed.

Vocational rehabilitation and future sick-leave.

The aim of the present pretest-posttest study was to examine and compare the impact of vocational rehabilitation on future sick-leave for employed and unemployed people, respectively, on long-term sick-leave. The study is based on 416 registered long-term sick-leave cases that were initiated during 1992-94 in the city of Stockholm, and that became objects for vocational rehabilitation. The hypotheses were (1) that the number of sick-days and levels of benefit for both employed and unemployed would be less after rehabilitation than before and (2) that rehabilitation would affect employed people more than unemployed people. The hypotheses are supported in that both employed and unemployed have less sick-days and lower levels of benefits after vocational rehabilitation than before and that unemployed people have more sick-days and higher levels of benefits than employed people after rehabilitation. However, since unemployed people also have more sick-days before rehabilitation, the proportional decrease is about the same. Another finding was that men, especially among the unemployed improved more than women.

The effect of vocational rehabilitation on later sick leave.

PURPOSE: The aim of this study was to examine the effect of vocational rehabilitation on later sick leave for employed and unemployed people on long-term sick leave. METHOD: The study was based on long-term sick-leave cases initiated during 1992-1994 in Stockholm, Sweden. Of 1704 cases, 383 (321 employed and 62 unemployed) underwent vocational rehabilitation. These were individually matched with sick-leave cases not undergoing rehabilitation, using the variables age, sex, diagnoses and employment status. RESULTS: The hypotheses were (1) that people who underwent rehabilitation, both employed and unemployed, would have less later sick leave than those who did not, and (2) that rehabilitation would affect employed people more than unemployed people. These hypotheses were only partly supported. CONCLUSIONS: The results indicate that vocational rehabilitation has a positive effect regarding later sick leave only for unemployed men. For unemployed women the effect is negative and for those employed, both men and women, rehabilitation has no demonstrable effect.

Return to work following vocational rehabilitation for neck, back and shoulder problems: risk factors reviewed.

PURPOSE: The present aim was an overview of factors associated with return to work following vocational rehabilitation for problems in the neck, back, and shoulders. METHOD: Studies were identified through a systematic keyword search in databases. For inclusion, return to work had to be in focus and studies to have been published between 1980 and 2000. RESULTS AND CONCLUSION: A great number of demographic, psychological, social, medical, rehabilitation-related, workplace-related and benefit-system-related factors are associated with return to work. The different types of risk factor are associated in many ways. People with greater chances of job return after vocational rehabilitation are younger, native, highly educated, have a steady job and high income, are married and have stable social networks, are self-confident, happy with life, not depressed, have low level of disease severity and no pain, high work seniority, long working history and an employer that cares and wishes them back to the work place. Unfortunately, people with the above profile are seldom found among the long-term sick.

Mobility, muscular strength and endurance in the cervical spine in Swedish Air Force pilots.

PURPOSE: Muscle strength, endurance and range of movement of the cervical spine in a group of Swedish Air Force jet pilots (AF) and in a reference group of conscripts doing their military service (RG) were compared. METHODS: We tested 30 (AF) 24-42 yr and 33 (RG) 19-22 yr. A questionnaire was used to document complaints. Maximum voluntary isometric muscle strength of the flexor and extensor muscles of the cervical spine and sub-maximum isometric endurance in the flexor and extensor muscles were measured. RESULTS: Eleven AF (37%) and four RG (12%) had experienced discomfort in the neck within the previous year. The pilots' flexor and extensor muscle strength (47 Nm and 65 Nm) was superior to that of the conscripts (36 Nm and 59 Nm) (p = 0.0001, p = < 0.05, respectively). However, the RG group had greater isometric endurance in the flexor muscles than AF (p = < 0.05) and greater neck rotation (p = <0.005). There was no difference between the two groups in the other variables. CONCLUSION: Differences between the groups with regard to muscle strength and endurance might depend on variations in work-related physical muscle strain, and/or differences in fiber composition in the muscles, which might be reflected by pilot selection procedures.