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Biomedical subjects

J Borg

Publications and source records attributed to J Borg.

At least 73 records · Page 4Linked to original sources
PubMed1987

Sensory involvement in distal myopathy (Welander).

Eleven patients with Welander distal myopathy were subjected to detailed sensory testing including measurements of perception thresholds for vibration and temperature in both hands and feet. The threshold values were compared with normal, age-corrected values and also with data from an age-matched control group consisting of patients with antecedent poliomyelitis with the same degree of paresis. The screening examination indicated impaired thermal sensibility in all 11 patients and impairment for at least one other sensory modality in 9 patients. In comparison with age-corrected normal values, the measured warm-cold difference limen was abnormal in the feet of 9 patients and the vibratory threshold at least at one test point in 6 patients. When compared with the data from the paretic controls, the thermal abnormality was significant with regard to warm and cold thresholds, the warm-cold difference limen and the heat pain threshold. The vibration threshold abnormality was significant in the feet. It is concluded that sensibility impairment is present in Welander's myopathy indicating a peripheral sensory neuropathy involving both unmyelinated (C-fibers) and myelinated fibers.

Aged↗
PubMed1987

Muscle biopsy findings, conduction velocity and refractory period of single motor nerve fibres in schizophrenia.

Eight untreated and eight neuroleptic treated male schizophrenic patients were studied. Light and electron microscopical analysis of muscle biopsies from the anterior tibial muscle showed a spectrum of pathological changes without significant quantitative or qualitative differences between the two groups. The changes included atrophic fibres, central nuclei, "moth-eaten fibres", "ring fibres", fibre splitting and subsarcolemmal and intermyofibrillar glycogen droplets. Electrophysiological investigation of single motor unit properties showed impaired peripheral impulse propagation in both patient groups while the conduction velocity and the refractory period of single motor nerve fibres were within the same range as in healthy subjects. In conclusion there are neuromuscular abnormalities in schizophrenic patients which cannot be attributed to medication or drug abuse.

Adult↗
PubMed1987

Conduction velocity and refractory period of single motor nerve fibres in antecedent poliomyelitis.

The axonal conduction velocity and the axonal refractory period were determined using electromyographic techniques for 60 single motor units in 11 patients with antecedent poliomyelitis. The results were compared with previous observations in healthy subjects as well as subjects with motor neuron disease. In antecedent poliomyelitis there was a reduced proportion of nerve fibres with low conduction velocity as compared with the findings in healthy subjects. The mean value of the axonal conduction velocities in antecedent poliomyelitis (42.4 +/- 3.7 m/s, M +/- SD) was significantly higher (p less than 0.01) while in motor neuron disease the corresponding value (35.2 +/- 7.8 m/s) was significantly lower (p less than 0.005) than in healthy subjects (39.8 +/- 4.9 m/s). In antecedent poliomyelitis the conduction velocity and refractory period were related as in healthy subjects while abnormally long refractory periods were observed in motor neuron disease.

Action Potentials↗
PubMed1987

Muscle fibre type composition, motoneuron firing properties, axonal conduction velocity and refractory period for foot extensor motor units in dystrophia myotonica.

Seven patients with dystrophia myotonica were investigated using neurophysiological combined with histochemical techniques to elucidate motor unit properties in foot extensor muscles, which are often involved in the early stages of this disorder. For the 25 extensor digitorum brevis motor units studied the axonal conduction velocity, the axonal refractory period and the voluntary firing properties were within normal limits. However, high threshold motor units were not observed and the mean value of the axonal conduction velocities was lower (p less than 0.02) for the dystrophia myotonica motor units when compared with corresponding data from healthy subjects. There were also signs of impaired impulse propagation in the terminal part of the motor unit. In muscle biopsy specimens from the anterior tibial muscle, fibre type composition and structure were demonstrated using enzyme histochemical techniques for adenosine-triphosphate and immunohistochemical techniques for identification of the types of myosin isoform present. The histochemical findings indicated a type I fibre dominance, which was most obvious in the more seriously affected muscles. Neonatal myosin was observed preferentially in small but also in some normal sized fibres. Furthermore, some ring fibres were present and these showed staining with antineonatal myosin in their superficial portion. This indicates that an abnormal regeneration is one cause of the myopathic appearance of the muscle fibres in dystrophia myotonica. These investigations show that there is a reduced proportion of type II motor units in foot extensor muscles involved in the myopathy in dystrophia myotonica although it cannot definitely be established whether this is due to a loss of high threshold type II motor units or type II to type I transformation.

Action Potentials↗
PubMed1986

Preferential glutamine uptake in rat brain synaptic mitochondria.

Glutamine uptake has been studied in purified rat brain mitochondria of synaptic or non-synaptic origin. It was taken up by an active saturable transport mechanism, with an affinity two-times higher in synaptic than in non-synaptic mitochondria (Km = 0.45 and 0.94 mM, respectively). Vmax of uptake was 7-times higher in synaptic mitochondria (Vmax = 9.2 and 1.3 nmol/min per mg protein, respectively). Glutamine transport was found to be inhibited by L-glutamate (IC50 = 0.64 mM) as well as thiol reagents (mersalyl, N-ethylmaleimide). It is suggested that differential uptake of glutamine in mitochondria of synaptic or non-synaptic origin may be a major mechanism in the regulation of the synthesis of the neurotransmitter glutamate.

Animals↗
PubMed1986

Measurement of lean body mass and total body fat using dual photon absorptiometry.

We describe a method for measuring the lean body mass (LBM) and total body fat (FAT) by dual photon absorptiometry (DPA). A total body rectilinear scan was employed with a radiation source of 1 Ci 153Gd. The reliability of estimating the lean percent was assessed in vitro using limb phantoms consisting of ox muscle, lard, and human bone. The precision and accuracy in vitro of the lean percent determination were 1.5% and 1.9%, respectively. The accuracy error in vivo of measuring the total mass of soft tissues (TMST) was approximately 1.4%, thus yielding an overall accuracy error of the LBM of about 2.5%. The precision in vivo of the lean percent and the LBM in kg of duplicate measurements on five healthy subjects was 2.5% and 2.2%, respectively. Other estimates of the LBM and FAT, ie, the calculation according to Boddy et al6 and the skinfold thickness measurement (triceps and subscapular), were compared to the DPA measurement in 100 healthy subjects. High correlations were found between the FAT or FAT% by DPA versus (1) the FAT or FAT% calculated according to the formulae of Boddy et al, and (2) the skinfold thickness. The correlations between the FAT and FAT% by Boddy et al and the skinfold thickness were, however, moderate. The correlation between LBM by DPA and LBM by Boddy et al was highly significant (r = 0.96, SEE = 4.4%). We conclude that LBM and FAT measurements using DPA have precision and accuracy errors that are commensurate with a reliable estimation of the gross body composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1986

Representativity of regional to total bone mineral in healthy subjects and 'anticonvulsive treated' epileptic patients. Measurements by single and dual photon absorptiometry.

Dual photon (153Gd) and single photon (125I) absorptiometry were used to measure the regional bone mineral content (BMC) and density (BMD), as well as the total body mineral content (TBBM) and density (TBBD), in sixty-nine healthy subjects and in twenty-three epileptics on phenobarbitone. The BMCs (and BMDs) of all regions were significantly correlated to each other and to the TBBM (and TBBD). No difference in the ability to discriminate between the different study groups was found for the various regions, excepting the BMD of the head. The relationship between the forearm BMC and TBBM was highly significant, and identical in the five groups. The relationships between spinal BMC and forearm BMC, and TBBM differed in the five groups. It is concluded that some local measurement may be used as estimates of the total body bone mineral in some groups of patients with minor metabolic bone disease and healthy subjects.

Adolescent↗
PubMed1985

Selective culture of neurons from rat cerebral cortex: morphological characterization, glutamate uptake and related enzymes during maturation in various culture media.

Dissociated cerebral cortex of fetal rat was grown in a serum-free, chemically defined medium (CDM) (containing insulin, progesterone, estradiol, transferrin, putrescine, selenium and 15 mM KCl) and compared with cultures grown in a medium containing 20% fetal calf serum (SCM). Neurons survived well using either medium, but in the serum-free medium the cellular population was exclusively neuronal (at 96%), while glial cells began to proliferate after one week in the SCM. The various cellular morphologies are described in the present report and the presence of immunological markers characteristic of neurons was investigated. Autoradiographic experiments have been performed after incubation with various putative neurotransmitters and we have shown the presence of a strikingly high proportion of glutamatergic neurons in these cultures. Glutamate high affinity uptake was also greatly increased in neuronal cultures maintained in a CDM compared to a SCM, especially in young cultures. The development of different enzymes involved in the metabolism of glutamate was also studied; the specific activity of glutaminase increased in culture and was found to be higher in a CDM than in a SCM, while the inverse was true for glutamine synthetase. The relative proportion of both enzymes in neurons compared to glial cells was opposite, as neuronal cultures had higher levels of glutaminase and glial cultures were enriched in glutamine synthetase activity. It seems that the proportion of glutamate-neurons increases when cultured in a CDM compared to a SCM and we suggest that this culture procedure may provide a purely neuronal population enriched in mature glutamatergic neurons. It may thus be useful for future in vitro studies on glutamate and GABA metabolism in neurons.

Animals↗
PubMed1985

A comparison of two methods to measure the recovery of nerve fibre excitability.

A methodological study was performed on single myelinated dorsal root fibres of rats. The recovery of excitability following a conditioning electrical stimulus delivered through the same electrode as the test stimulus and following a conditioning propagated nerve impulse were compared. Using low test stimulus strength, the recovery time permitting a propagated test impulse was 2.31 +/- 0.72 ms (mean +/- SD) after a conditioning electrical stimulus and 1.96 +/- 0.78 ms after a conditioning propagated impulse (P less than 0.001). The difference and its significance for clinical refractory period measurements are discussed.

Action Potentials↗
PubMed1985

Comparison of single- and dual-photon absorptiometry in postmenopausal bone mineral loss.

We describe a single photon absorptiometric (SPA) technique, which enables differential estimation of the rates of loss from trabecular and cortical bone. Ten scans are obtained in the forearm: six in an area with about 7% trabecular bone and four scans in the adjacent distal area with a trabecular bone content of 25%. By comparing bone masses of these two sites in 19 postmenopausal and 53 premenopausal women, the postmenopausal trabecular bone loss was estimated to be approximately seven times greater than cortical loss within the first years of cessation of regular vaginal bleeding. On a group basis the bone loss at the distal forearm scan site (by SPA) corresponded closely to the spinal bone loss (by dual-photon absorptiometry). The reproducibility of the two scan sites in the forearm was 1-1.5% (CV%), which makes the method suitable for longitudinal studies. Corrections for variations in fatty tissue covering can be made without deterioration of the reproducibility. The high precision can only be achieved with a good calibration procedure; if calibration is not done the reproducibility error increases two- or threefold.

Adult↗
PubMed1984

Total body bone mineral in vivo by dual photon absorptiometry. I. Measurement procedures.

A dual photon scanner using a 1 Ci 153Gd source, a NaI detector, traditional electronics and a desktop computer, was constructed. Software for the computation of the total body bone mineral (TBBM) was developed. Non-linear influences such as deadtime due to high count rates, patient scatter and Compton effects were investigated and correction algorithms were introduced in order to obtain exponential attenuation. System precision was measured on a bone-aluminium standard (CV = 2.6%) and system linearity was assessed on aluminium pieces (r = 0.999, SEE = 3.0%). Short-term precision in vivo was tested on 15 healthy subjects scanned twice with a 2-month interval (CV = 2.4%). Long-term reproducibility in vivo was tested on two healthy subjects scanned eight times with 1-month intervals (CV = 1.9% and 3.2%). The influence of patient orientation was investigated on two skeletons. No significant difference was found between anatomical and random orientation. It was concluded that the precision errors were small, therefore making the method applicable not only in cross-sectional studies but also in longitudinal studies designed to investigate the loss or gain of total bone mass in patients suffering from calcium metabolic disorders.

Bone and Bones↗
PubMed1984

Total body bone mineral in vivo by dual photon absorptiometry. II. Accuracy.

We investigated the accuracy of total body mineral (TBBM) measured by dual photon absorptiometry (1 Ci 153Gd source, 44 and 100 KeV) using skeletons, soft tissue equivalent materials and whole cadaver extremities. The accuracy was assessed on five skeletons (r = 0.99, SEE = 1.5%). The influence of the soft tissue composition on the TBBM measurement was investigated in the same five skeletons. They were scanned in a 16 cm thickness of ethanol solutions of different concentration (0, 20, 40, 60, 80, 100% ethanol) and only a 2% difference (non-significant) was found between measuring 100% ethanol and 100% water. Furthermore, seven whole cadaver extremities were scanned before and after removal of the soft tissues (r = 0.995, SEE = 6.3%). The slope was not different from one and the intercept not different from zero. Equipment at the University of Wisconsin, Madison, and at Glostrup Hospital, Denmark, was compared by measuring the same healthy subjects and skeletons on both scanners. The Glostrup and Madison TBBM values correlated well (r = 0.99, SEE = 5.8%) and the intercept (345 Glostrup arbitrary units) was not significantly different from zero (P greater than 0.05). The TBBM results were calibrated into total body calcium (TBCa) and no significant difference was found between Glostrup and Madison TBCa values (P greater than 0.20).

Bone and Bones↗
PubMed1984

Refractory period of single motor nerve fibres in man.

Electromyographic single motor unit recordings were used to study the axonal refractory period of 28 accessory nerve innervated motor units in young normal subjects and 10 reinnervated motor units in elderly subjects. The refractory period was measured after a conditioning antidromic propagated nerve impulse and after a conditioning electrical nerve stimulus delivered through the same electrode as the test stimulus. The refractory period after a propagated impulse was 1.83 +/- 0.26 ms when test stimulus strength was 10% above the axonal threshold at rest and 0.88 +/- 0.26 ms when test stimulus strength was 100% above threshold. Corresponding data after an electrical stimulus were 2.38 +/- 0.32 ms and 1.28 +/- 0.22 ms. The difference between the methods was partially due to the effect of stimulus spread when the refractory period was measured after an antidromic propagated nerve impulse. Different properties of the nerve fibre membrane and the surrounding tissues after a propagated nerve impulse and after an electrical stimulus might also contribute. For further studies of motor unit pathology both methods seem equally reliable when proper normal data are available.

Adult↗
PubMed1984

Conduction velocity and refractory period of single motor nerve fibres in motor neuron disease.

Electromyographic single motor unit recordings were used to study the axonal conduction velocity and the axonal refractory period of 60 motor units in patients with severe motor neuron disease. Eighteen per cent of the motor units had abnormally low axonal conduction velocity probably due to secondary degenerative changes. Thirty-two per cent of the motor units had abnormally long axonal refractory period but normal conduction velocity. Whether this reflects a primary disease mechanism or secondary changes remains to be established.

Adult↗
PubMed1983

Cysteine sulfinic acid uptake in cultured neuronal and glial cells.

The presence of an efficient high affinity uptake system for L-CSA has been demonstrated in cultured neuronal and glial cells of various types. In neurons and most glial cells L-CSA uptake is inhibited by acidic amino acids, L-glutamate and L-aspartate and requires sodium ions; however the sodium dependence varies from one cell type to the other. The characteristics of the uptake system change during cell maturation, especially in astroblasts. The predominance of CSA uptake in glial cells as compared to neurons, the similarity of the kinetic parameters and of the structural specificity of L-glutamate uptake suggest that both excitatory amino acids are transported by a common system. In view of accumulating evidence, the present results are in agreement with a role of CSA as a neurotransmitter and as a precursor for taurine biosynthesis in the central nervous system.

Animals↗
PubMed1983

Relationship between local and total body bone mineral in epileptic patients and normal subjects.

Total body bone mineral (TBBM), measured by dual photon absorptiometry, and local body bone mineral content (BMC), measured by single photon absorptiometry, in both forearms were determined in 49 epileptic patients, 19 receiving phenytoin and 30 receiving carbamazepine, and in 55 controls. A highly significant correlation was found between BMC and TBBM in the patients (r = 0.81, SEE = 10.6%), as well as in the controls (r = 0.78, SEE = 9.9%). Furthermore, the intercepts and the slopes were virtually of the same order. The patients on phenytoin had a mild generalised osteomalacia, independent of method used, whereas the patients on carbamazepine did not have this side-effect. It is concluded that BMC of the forearm can be used as a valid estimate of total body bone mineral in groups of epileptic patients and in normal subjects.

Adult↗
PubMed1983

The fatigue of voluntary contraction and the peripheral electrical propagation of single motor units in man.

1. Single human motor units from the short extensors of the toes were classified by their voluntary threshold and axonal conduction velocity. The voluntary discharge intervals, and the shortest discharge intervals at which action potentials were conducted to the muscle fibres, were studied during maximal voluntary effort maintained for 1 min, and were compared with the intervals calculated to be necessary for full fusion.2. Electromyographic techniques were used. High selectivity of the recordings was obtained after blocking of the main motor nerve with lidocaine in subjects with an accessory innervation of just a few motor units or 6 months after lesions to intramuscular nerve twigs, when the muscle-fibre density within the motor units was increased.3. For a whole minute of maximal voluntary effort, motor units with low threshold and low conduction velocity fired tonically at a rate that should have been sufficient for maximal tension. These intervals were longer than the intervals at which blocking occurred.4. In ordinarily motivated and untrained subjects, motor units with high threshold and high conduction velocity fired tonically at intervals sufficient for full tension for some seconds. Under these circumstances the voluntary intervals were longer than the critical ones.5. Through extraordinary motivation and training, motor units with high threshold and high conduction velocity could also be driven tonically for 20-60 s at the high rates required for full tension. The critical intervals then approached the voluntary ones. Blockings occurred and increased in frequency as the contraction continued.6. When motor units with high threshold and high conduction velocity were tetanized electrically at 20 Hz, which was the lowest discharge rate of these units in tonic voluntary contraction, blockings occurred within 60 s.7. The role of the peripheral block is discussed in relation to loss of tension in prolonged voluntary contraction.

Action Potentials↗